Little is known about Saitama's past, but it is known that he lives in his apartment by himself. According to Saitama, as a child he used to watch superhero shows many times, and wishes that he wants to be like those heroes someday.
Middle School Year
In his second school day of his first year in middle school, Saitama is seen reading a health and PE manual, but did not hear from the other students about what happened to the freshman who called himself "The Bicycle Commuter" yesterday, after two third-year bullies beat him up pretty badly.
After school on a rainy day, Saitama is watching a news about the ongoing monster incident in Z-City and its increase in the last decade. Saitama drifted off to sleep, but forgot to do his homework. As a result, he is called by his homeroom teacher to the teacher's room, despite suggesting that he could do both days' homework that night.
While going to the teacher's room, he is interrupted by the same two third-year bullies from the day before and they threatened him to hand over his wallet, but Saitama told them he doesn't have one and prepares to fight them instead. However, Saitama is still too weak to defend himself from the bullies and his 200 yen was stolen by them. Shortly after, Piggy Bancon attacks the bullies and takes Saitama's stolen money from them. Saitama soon heard that one of the bully's reason in threatening the freshmen to steal their money was to feed his little brother his lunches, and Saitama goes chasing after the pig monster to get his money back, but due to his lack of strength, is unable to retrieve his 200 yen. After the monster is killed by the police and special unit forces, Saitama decides to return to school and see his homeroom teacher.
Saitama is then scolded by his homeroom teacher, while trying to tell what happened to himself back before going to the teacher's room, though the teacher thinks Saitama is lying. While going home, Saitama becomes very disappointed in himself for being weak and losing many times, and starts to think about himself and his future.
Adult Year, First Hero Act
Three years prior to the start of the story line, Saitama was an unemployed man on a job hunt. Before becoming unemployed, Saitama was working part time in a convenience store. On one occasion, there was a robber entering the convenience store. Despite there being a man pointing a knife at Saitama, all Saitama did was wonder where the barcode was, believing that the knife was one of the merchandise. One day, after yet another failed interview, a nihilistic-feeling Saitama was wandering the streets and encountered Crablante. Saitama's total apathy toward the situation impresses Crablante, who claims to share a similar outlook, prompting him to spare Saitama and move on. Crablante tells him that his real prey is a child with a cleft chin anyway.
Walking on, Saitama spots the child Crablante was talking about. He decides that he doesn't want anything to do with the matter but after Crablante suddenly arrives, Saitama impulsively saves the child from Crablante's attack. He urges the child to run away and demands to know why Crablante wants the boy dead. While Crablante explains the prank the boy pulled on him, Saitama chuckles and notes aloud how the monster resembles one from an anime Saitama watched in his youth. This enrages Crablante, who pummels Saitama even after the latter resolves to live out his childhood dream of being a superhero by fighting back. As Crablante turns from the apparently defeated Saitama to finish the cleft-chinned boy, Saitama lassos one of his eye stalks with the loop of his removed tie and tears it out. The monster is defeated and the child saved. Unknown to him, the child told his grandfather about the incident and decided to create the Hero Association in Saitama's honor for saving his grandchild from the monster's crime.Resolving after this encounter to become a mighty superhero, Saitama started a daily training schedule which consisted of 100 push-ups, 100 sit-ups and 100 squats along with running 10 km every single day. He ate three meals a day, but only a banana as breakfast and also didn't use the air conditioner to strengthen his mental resistance. These daily activities were extremely tough and caused his body excruciating pain, muscle aches, and vomiting blood. However, Saitama didn't give up and continued his training day after day.
Personification of A Light Pull Cord Attack
On Saitama's 300th day of training, his body had already felt the effect of working out too much. However, Saitama has shown signs of improvement, such as wrecking a car after saving a boy from an accident. At that time, the Personification Of A Light Pull Cord attacked the streets, looking for an opponent that would satisfy him.
The monster punches cars and buildings as he keeps searching. To test the fruits of his labor, Saitama challenged the monster but was sent flying after a single punch. Filled with determination to overcome his limits, the monster punches Saitama again and is knocked down. However, Saitama quickly got up, and spat out a tooth that had been bothering him because of a cavity.
Saitama then defeated the monster with a single punch before moving on with his workout.
King's BeginningAt some point in the first year and a half of Saitama's training, the Octopus Claw Man attacked an unspecified group of people. Saitama arrived and defeated the Octopus Claw Man, though sustained multiple injuries from the fight. After the fight, he consoled one flailing civilian who had suffered three scratches above his left eye from the mysterious being. When questioned about his injuries, Saitama shrugged it off, simply smiling at the thought that there was a special sale that day.
Magicicada Larva Attack
Some time between when Saitama started training and started to lose his hair, Z-City experienced a Mysterious Being attack by the 170,000-Year Magicicada Nymph, prompting the citizenry to evacuate to the state-of-the-art Shelter Nr. 7. The three low-ranking heroes sent to defeat the Magicicada were defeated, but survived and managed to find some straggling evacuees on their way back to the shelter, among them being Saitama.
When Saitama discovers that he has been led to a shelter, he became upset, stating that he thought that following the heroes would lead him to the Mysterious Being. Saitama attempts to leave so he can find the Mysterious Being, but is restrained by the citizens, thinking he's become suicidal. The guard attempt to explain that the doors can't be opened while the disaster is still ongoing, but reassure the public that the shelter is able to withstand any sort of attack. While she praises the structure's perfection, Saitama confronts her again to ask where the bathroom is, only for her to reply that the 'perfect' shelter was nevertheless designed and built without bathrooms.
Saitama slowly becomes more and more distressed, as he doesn't know if his bladder can hold until the situation ends. After overhearing that two A-Class heroes were defeated by the beast, and that it will take three hours for a Hero Association squadron to arrive, Saitama can't take it anymore. He walks to a wall of the shelter and breaks a hole in it with a single punch before the stunned onlookers, and runs off stating that he's going to the convenience store. Just as he is about to reach the store to use the bathroom, the 170,000-Year Magicicada Nymph appears in front of him, which he promptly kills.
One and a half years after he started training, he had lost his hair and became strong. He continued his training for another year and a half before starting his superhero career.
Saitama Introduction Arc
Saitama appears at the scene just in time to save a young girl from being killed. The monster is angered and asks who Saitama is, and he replies that he is "just an average guy who serves as an average hero". After reluctantly listening to the monster's angry monologue and watching its transformation, Saitama kills it with a single punch. After this, he screams out in frustration at another easy victory.
Some time after, Saitama hears about a Demon-level disaster emergency, stemming from the The Brain and Brawn Brothers destruction of D-City. After finding the duo, Saitama leaps onto the monstrous Marugori's shoulder and tells him to put some pants on. Fukegao, Marugori's brother who is on his other shoulder, is shocked by Saitama's sudden appearance and orders his brother to swat him. However, Marugori absentmindedly swats at the wrong shoulder, instantly killing his brother. Enraged, Marugori grabs Saitama and throws him into the ground. Saitama is unaffected, but Marugori continues with a frenzied assault of massive stomps and punches, creating a large crater. Believing he has killed Saitama, Marugori moves away, only for the completely unfazed Saitama to dash out of the crater and crumple the giant's face with a single punch. Saitama states that having an overwhelming power is boring, as the Marugori topples over. Unfortunately, Saitama's blow causes him to fall on top of B-City and the town is destroyed.
After defeating the giant, he returns home at night when he was noticed by a mysterious being, revealing himself to be Super Custom YO649Z Mk. II. While Super Custom YO649Z Mk. II brags about his love to build custom cars so much that he decked himself out and turned into a custom car-loving monster, Saitama just stares at him and the monster insults his bald head, prompting Saitama to strike him with a single punch, killing the monster.He is later attacked by the Subterranean People, who destroy his apartment and give him his first real fight in years. Just as he is about to face their leader the Subterranean King it is revealed to be a dream. When the real Subterranean King invades Saitama kills him instantly and his people give up and retreat.
House of Evolution Arc
Saitama is lamenting his life: how every fight ends with a single punch and goes on to compare all his battles to swatting insects. As if to illustrate the point to himself, he delivers a mighty swat to a mosquito that has landed on his hand, but when he lifts up his hand the mosquito flies away unharmed. After unsuccessfully swatting at it several more times, it flies off and Saitama is left in a rage. The mosquito is then shown to fly off to Mosquito Girl. Before this event, Saitama saw a news story about a mass mosquito outbreak that is headed towards Z-City, and showns slight concern.
When Mosquito Girl raids the city, Genos appears and starts to fight her and performs well for a while, but then she begins absorbing all the blood gathered by her mosquitoes. Saitama suddenly comes running around a corner on to the battlefield, in pursuit of the mosquito he'd been trying to kill. At that moment, Mosquito Girl finishes her blood-fueled evolution and sends her mosquitoes crashing down on Saitama and Genos, the latter of whom obliterates them all with a gout of flame. When the smoke clears Saitama is standing there naked and only slightly singed, thanking Genos for killing the mosquitoes.
The newly empowered Mosquito Girl starts attacking Genos and tearing him apart with her claws. Just as the heavily damaged Genos is about to resort to self-destructing, Saitama suddenly slaps Mosquito Girl, sending her flying through a nearby building and into the sky. Dusting off his hands, Saitama states that he hates mosquitoes. After witnessing Saitama's incredible power, Genos asks Saitama to make him his apprentice.
At Saitama's house, Genos gives a long explanation of his past and motives, but Saitama is completely uninterested. Saitama agrees to take Genos on when he explains that he simply wants to be taught to become as strong as Saitama.
Meanwhile, the House of Evolution, having become interested in Saitama after he defeated their warrior Mosquito Girl, sends more of its creations to attempt to capture him. Kamakyuri arrives at Saitama's house first, crashing through the ceiling and immediately has his head punched off for the trouble. Saitama and Genos then go outside to meet the threat where they are confronted with Frog Man and Slugerous. Saitama promptly buries their heads in the ground complaining about how they made a hole in his ceiling. Suddenly, a hand emerges from the ground by Saitama's foot, grabbing his leg and dragging him underground, until only his head protrudes from the sidewalk. Genos begins to rush to Saitama's aid but is intercepted by Armored Gorilla. While Genos is fighting Armored Gorilla, Saitama is approached by Beast King.
Beast King congratulates Ground Dragon on incapacitating Saitama, but notices that the unfazed hero is falling asleep due to how pleasantly temperate he found it underground. Beast King starts to get angry and threatens to scratch Saitama's eyes out, at which point Saitama simply steps free out of the ground. Beast King then attacks Saitama, who easily avoids his claws and slicing air currents, one of which kills Frog Man and Slugerous. Beast King is enraged that none of his attacks are hitting and goes berserk, sending a flurry of attacks at Saitama, who dodges them all before striking back with a short combo of punches. The attack obliterates Beast King's entire upper body, prompting a terrified Ground Dragon to run away by digging underground, but Saitama appears in front of him through a hole of his own making and punches Ground Dragon through the earth and up into the sky. When Saitama gets back to the surface, he finds that Genos has defeated Armored Gorilla and is questioning him. After Saitama shows Armored Gorilla the remains of Beast King he tells them all they want to know. 
Roughly four hours later, Saitama and Genos have climbed a forest path to arrive at the House of Evolution's base. Wasting no time, Genos destroys the above-ground portion of the base with an energy blast, surprising Saitama slightly with his ruthlessness. In the rubble they nonetheless find a metal door which leads to the basement. As they enter the subterranean portion of the lair, they are attacked by Carnage Kabuto, who discards his former 'master' Dr. Genus before embedding Genos into a wall and incapacitating him with a single, thunderous blow. Saitama is angered because Carnage Kabuto turned Genos into "modern art" and agrees to Carnage Kabuto's request for a fight.
The fight is about to start when Genos re-appears and attempts to fight Carnage Kabuto, but is beaten down again causing Saitama to step in to fight. Carnage Kabuto comments on how he can feel that Saitama is really strong, while Saitama tells him not to disappoint him, as he expects Carnage Kabuto to be the strongest being from the House.
Suddenly moving with tremendous speed, Carnage Kabuto appears behind Saitama and is about to strike him, but suddenly becomes extremely intimidated and leaps back, thinking to himself that if he had attacked at that moment he would have been killed. He explodes with rage and fear and orders Saitama to tell him how he got so strong. Saitama agrees to tell them and explains his method of 100 sit-ups, push-ups and squats and 10km of running every single day. Genos is outraged, stating that Saitama's strength would be totally impossible to achieve with that kind of routine strength training, while Carnage Kabuto is angered, thinking Saitama is mocking him.
Enraged, Carnage Kabuto enters "Carnage Mode" and states that he'll stay in this form and go on an uncontrolled rampage for a week, "until next Saturday". Carnage Kabuto then begins to pummel Saitama, sending him flying around the room. While this is going on, Saitama comes to the horrifying realization that if "Carnage Mode" lasts for a whole week ending on a Saturday, then it is in fact Saturday that day and thus he missed the "special sale day". Overcome with despair, he cries out and obliterates Carnage Kabuto with one punch. Genos then informs him that they still have sometime if they hurry, so he smashes a hole in the wall and rushes to the store.
Paradise Group Arc
Saitama is first seen waking up frantically from a dream involving someone pointing a snotty finger at him. Realizing it was just a dream, he then turns on the news and finds out that the criminal Hammerhead and his terrorist organization known as the Paradisers, consisting entirely of bald, dangerous looking men have arrived and started wreaking havoc. The news warns everyone to avoid any bald men with a dangerous aura. This angers Saitama who states that this group will ruin his image as everyone will mistake him for a villain. He resolves to destroy the Paradisers to protect his image. Saitama heads out to search for the villains, and on his way many people end up mistaking him for members of the Paradisers.
On his search for the Paradisers, Saitama finds himself lost in a forest. Trying to find a path out, he is halted when Hammerhead, recently defeated by the powerful ninja Speed-o'-Sound Sonic, appears rushing towards him. Hammerhead mistakes Saitama for someone wanting to join up with the Paradisers, and Saitama tells him that he actually came to destroy them. Hammerhead swiftly attacks Saitama with a vicious punch, but Saitama is unfazed and unimpressed. Enraged, Hammerhead charges up to full power and executes his Windmill Attack. Upon seeing this Saitama notices it looks much like an 'attack' he used to perform as a kid and wonders if Hammerhead is similar to him. He then stops the attack with little effort and shatters Hammerhead's battle suit with a quick punch. After making him promise to never do bad things again, Saitama allows Hammerhead to flee.
Shortly after, Speed-o'-Sound Sonic arrives demanding to know where Hammerhead has gone. Saitama points in the direction that Hammerhead fled. Sonic then attacks Saitama, mistaking him for a member of the Paradisers, with a kunai thrown at lightning fast speeds. However Saitama effortlessly catches both the kunai and Sonic's subsequent attack with a sword and then proceeds to break the sword in half. Saitama then frantically explains that he is not a member of the Paradisers and asks Sonic whether or not he recognizes him as the man who has saved the world many times. When Sonic denies knowing him, Saitama becomes severely disheartened. Sonic then proceeds to attack Saitama, stating that the real problem is that Saitama was able to see two of Sonic's attacks and that his pride cannot allow for Saitama to live. Upon hearing this, Saitama accuses Sonic of being a liar stating that Sonic just wants to test his attacks on him, indicated by the "childlike smile" on Sonic's face.
After Sonic jumps around for quite some time, Saitama intercepts him and asks if he can go home now. Surprised, Sonic retaliates with a Wind Blade Kick, but Saitama attempts to interrupt his attack by placing his fist directly in the path of Sonic's groin. However he accidentally moves his fist too far and taps Sonic's groin. Clearly in pain, Sonic swears that he will train day and night for their rematch and then flees.Later, Saitama is seen at his house going over the day's events with Genos. Saitama asks Genos to leave, stating that he is in shock due to a certain event that occurred that day. Genos, worried about anything that might shock Saitama, asks what it was and Saitama explains that he can't believe that Sonic had no idea who he was despite all his previous exploits. Genos then asks if Saitama was a registered superhero, which Saitama replies that he's not. Genos goes on to explain that anyone who hasn't registered with the Hero Association will never be recognized for their feats. Saitama resolves to become a licensed hero so he can achieve the fame he deserves. He asks Genos to register with him in exchange for formally accepting the latter as his disciple.
Hero Association Saga
National Superhero Registry Arc
Saitama arrives at the 6th Official Superhero Certification Exam Center and begins a series of physical tests. Saitama does so well on physical tests that he awes the examiners and disheartens the up and coming heroes from taking the tests altogether. Later in the waiting room, Saitama meets with Genos and the two discuss the easiness of the superhero qualification tests and state that there is no way they didn't pass. When the results of the tests arrive it is revealed that Saitama barely passed, having achieved a score of 71 when the passing is 70, and receives the C-Class hero designation. Despite this, Saitama achieved a perfect score in all the physical tests and broke every record of the Hero Association and the only reason his score was so low was because he did poorly on the written test.
Later, during a lecture from an A-Class hero Sneck, Saitama is seen chewing bubble gum, seemingly bored. This angers Sneck and, along with hearing the news that Saitama could quickly surpass him, causes Sneck to ambush Saitama but is quickly defeated though non-lethally.
Sometime, Genos apparently requests a sparring match with Saitama. Saitama having earlier agreed to take Genos as his disciple officially, under the condition that Genos register as a superhero as well, accepts his challenge. The battle begins with Genos firing a massive energy attack which Saitama dodges with ease. Genos proceeds to to attack Saitama physically, but eventually discovers he was chasing an afterimage the whole time. After an extremely close-range energy attack in which Genos believe he finally landed a blow on Saitama. Saitama, having dodged the attack and poking Genos' face, declares himself the victor, but Genos reminds him that the match cannot end until one of them is unable to continue. Upon hearing this Saitama appears in front of Genos and delivers a devastating blow that stops inches before hitting Genos' face. Though unharmed, the landscape behind him is obliterated. Saitama and Genos then return home.After the sparring match they head out to a shop, where they had an eating contest. While Genos had no problem eating, Saitama nearly passed out. Sweet Mask came and asked Genos to speak outside, with Saitama warning Genos about rookie crushing.
Five days later Saitama is seen lounging around his house reading a magazine. He notices Genos, carrying a huge backpack full of contents unknown, then requests to live with him. At first he declines, but after Genos tells him that he will pay him the rent Saitama allows Genos to stay with him.
Genos later informs Saitama that all C-Class heroes who are inactive for a week are removed from the official registry. Saitama, realizing he only has two days remaining, sets out to find a villain, only to discover that Z-City is completely peaceful. Saitama decides he will check again the next day and returns home. Upon discovering that Z-City is peaceful for the second day in a row, he becomes greatly distressed. All of a sudden, a kunai is thrown at Saitama, who catches it, and discovers that his would-be assailant is Speed-o'-Sound Sonic.
Saitama tells Sonic that he is busy and begins to walk away but Sonic rushes to intercept him. Frustrated, Saitama bites Sonic's sword, shattering it in the blink of an eye. He explains again that he is busy and threatens that, if Sonic gets in his way again, he will punch him. At this moment a woman from the crowd observes Saitama and states that he is a 'suspicious person'. Saitama, thinking that the woman was referring to Sonic, begins to lecture Sonic for being so violent. Then a C-Class hero, named Tanktop Tiger, explains that the woman was referring to him. Saitama explains that he is also a registered hero, but Tanktop Tiger states that he has no idea who Saitama is and thinks that he should leave as he is ruining the reputation of other heroes. Saitama becomes increasingly annoyed but, before he has a chance to attack, Sonic launches a surprise assault on Tiger, who is defeated instantly.
Sonic begins to wreak havoc on the surrounding civilians. During this chaos, Saitama saves a small boy's life by effortlessly moving a tree in place to intercept a falling car that would have killed the boy. Saitama, angered both by the fact that he can't find a bad guy to fight and that civilians are in danger, realizes that Sonic is now considered a bad guy and decides to retaliate. Saitama appears behind Sonic and dispatches him with a single swift chop. By defeating Sonic, he has saved himself from being removed as a registered superhero.
Rumored Monster ArcSaitama, apparently returning home from shopping, happens upon a scene where a Kombu Infinity had just defeated two A-Class heroes in battle. Upon seeing the monster, Saitama remembers that he forgot to get kombu and notices that the monster appears to be made of it. Later, Saitama is seen cooking kombu that was apparently taken directly from the monster's body, leaving it totally naked. Genos states that Saitama wanted to eat kombu to see if it could make his hair grow back.
Giant Meteor Arc
Saitama and Genos are relaxing in their apartment, and Genos tells Saitama that he's been promoted from C-Class Rank 388 to Rank 342, and while he hasn't been raised from S-Class Rank 17, he's been ranked 6th in popularity. Genos then gets a call from The Hero Association and heads out.
Later, after Genos fails to destroy the Meteor, Saitama shows up and asks Bang to take care of Genos. He then launches himself at the Meteor and punches through it, causing it to break apart. Unfortunately the pieces of the Meteor then rain down on Z-City. Saitama then lands, looks around and nonchalantly he settled the situation and walks off.
Three days later, Saitama and Genos are relaxing in their apartment, watching a news report on how the Meteor fragments destroyed many buildings and businesses in the city. After learning that his rank had jumped up from C-Class Rank 342 to Rank 5, Saitama gets excited and decides to go out for a walk around town. During his walk he gets called out by Tanktop Tiger, but Saitama doesn't remember who he is. Tanktop Tiger then declares that Saitama is a liar; that there is no way he would be able to destroy a Meteor on his own and that he merely took credit of the S-Class heroes work. Saitama starts to defend himself but is cut-off by Tanktop Tiger who calls out for his big brother, who then jumps in and introduces himself as Tanktop Black Hole.
Tanktop Black Hole claims that he has a perfect punishment for a "lying cheater" like Saitama. He then, in a rather loud voice, starts accusing Saitama of destroying the town. The commotion starts to attract citizens who begin to gather around the scene. Black Hole continues to accuse Saitama of destroying the town on purpose and slowly, the crowd begins to turn on Saitama, shouting out threats and accusations along with Tanktop Black Hole. Tanktop Black Hole then accuses Saitama of wanting to destroy the citizens, just as he "destroyed" the town, and then challenges him to a fight. Tanktop Tiger then rushes forward to attack Saitama, but gets easily knocked away into a pile of rubble, much to Tanktop Black Hole's surprise. Tanktop Black Hole then jumps in and tries to crush Saitama with his grip. Saitama intercepts him and locks hands with Tanktop Black Hole and squeezes, causing him to fall to his knees in pain and apologize for lying.Saitama then shouts to all the citizens that he did destroy the Meteor and that if anyone has a problem with him they should say it to his face. Some citizens move to accuse him of damage done to their property, but Saitama quickly shouts them down, telling them to blame it on the meteor, that he's not doing hero work because he wants to be admired by them but because it is something he wants to do, leaving his accusers stunned in silence.
Sea Monster Arc
On his way home, Saitama comes across a Seafolk about to attack a city, so he defeats it quickly. Some time later, Saitama is relaxing as Genos does dishes and explains that Saitama has advanced to the second rank of C-Class. He goes on to explain that once Saitama becomes rank 1, he can go up to B-Class. Genos then starts talking about how the top ranking C-Class hero hasn't left his position for around half a year, which apparently is no match for the top ranking B-Class hero. Before Genos can finish talking about that though, he gets a call about an attack on J-City by more Seafolk. They turn on the news and watch part of a news report on the incident and decide to head out to help.
Some time between their leaving and their getting there, Saitama and Genos get separated. During his search for the Deep Sea King, Saitama finds Mumen Rider's cell phone lying in the street.Upon picking it up, the man on the other end of the line requests to know who he is speaking to and, despite Saitama only being listed as a C-Class hero, decides to disclose the location of the Deep Sea King, apparently to finally determine just how strong Saitama is.
Later, Saitama arrives at the shelter just in time to witness Mumen Rider's defeat at the hands of the Deep Sea King. He catches Mumen Rider's unconscious body and tells him he fought well. He then observes the scene and is surprised to find that Genos is alive despite his grievous injuries. After remarking that he will quickly dispatch the Deep Sea King, Saitama is attacked by the monster, but he is noticeably unscathed.
The Deep Sea King declares his surprise that Saitama did not fall from his punch, but Saitama remarks that the monster's punch was simply too weak to hurt him. Meanwhile the spectators talk among themselves, telling each other that their situation has not changed at all with only a C-Class Rank 2 hero arriving. Deep Sea King starts to tell Saitama that he, as the ruler of mother sea, stands at the very top of the pyramid of all living organisms on Earth. Saitama, however, interrupts him and tells him to hurry up and fight. The Deep Sea King then quickly attempts to punch Saitama, only for Saitama to punch a hole in his body. As the Deep Sea King falls, Genos is seen smiling, and all the spectators stare on in disbelief.
Standing triumphant over the body of the Sea King, Saitama overhears the crowd of onlookers start to question the usefulness of the rest of the heroes who battled the monster. Not wanting the heroes' good reputation to be tarnished, Saitama remarks loudly that he got off lucky and that, if the other heroes hadn't weakened Deep Sea King before he arrived on the scene, he wouldn't have stood a chance. To further the credibility of his ploy, Saitama plays on the rumors of his underhanded nature by stating that, because he's the one who dealt the finishing blow, he'll get all of the credit for the victory regardless of the other heroes valiant efforts. Saitama's plan proves successful and the people's faith in the other heroes that participated in the battle is restored, while Saitama, on the other hand, grows more hated in the eyes of the citizens. Internally, Saitama reflects on how dull the battle with the Deep Sea King turned out to be.
Sometime after the battle with Deep Sea King, Saitama and Genos receive a box via airdrop from the Hero Association, containing several letters addressed to the heroes themselves. Upon opening the five letters that were addressed to him, Saitama discovers that the first three contain nothing but hateful words accusing him of cowardice and cheating, which angered Genos greatly but were disregarded by Saitama. The fourth letter contains a simple thank you message from an anonymous sender. The fifth letter turns out to be a letter directly from the Hero Association itself, notifying Saitama of his promotion to C-Class Rank 1, and inviting him to Hero Association Headquarters in Z-City.
Upon arrival at the Headquarters, Saitama requests to know why he was summoned to the headquarters and suspects that they called him there to reprimand him for his actions. His hosts, however, insist that the circumstances for which he was invited are quite the contrary and they congratulate him on reaching C-Class Rank 1. They then go on to inquire as to whether or not Saitama will move up to B-Class or remain in C-Class. Saitama expresses his apathy on the subject, but then goes on to state that he'd rather be B-Class, due to the fact that he would no longer have to report his weekly activities to the Association. He also reflects internally that he can't remain in C-Class forever, especially considering that Genos is already an S-Class. Other officials of the Association watching from a separate room question even the legitimacy of his exam results, to which one suggests that they allow him into B-Class to test that legitimacy: should he hold his own his power would be unmistakable, otherwise he will be broken by the factions in B-Class, in particular the Blizzard Group. Finally, they consult Sweet Mask for the verdict; Sweet Mask, finding neither significance in promotions from C-Class to B-Class nor anything noteworthy in Saitama's impression, allows it.
Later on, Saitama is walking home from headquarters, examining the official document declaring him a B-Class hero, when a delightful smell from a small oden shop draws him inside. Upon entering, Saitama orders an assorted oden and takes a seat at the counter where he is asked by another patron in the shop if he will have anything to drink with his oden. The patron then states that, if Saitama won't order a drink, then he will treat him to one. Upon observing this stranger, Saitama discovers it is none other than a bruised and battered Mumen Rider. Saitama questions why Mumen Rider would want to buy him a drink, to which Mumen Rider states that, if for nothing else, it would be to celebrate Saitama's promotion to B-Class and also reveals himself to be the sender of the "Thank You" letter that Saitama received. Upon finally recognizing the man as Mumen Rider, who he saved from the Deep Sea King, Saitama accepts his offer and orders a mozuku. Some time afterwards Saitama would rank up from 101 to 63.
Alien Conquerors Arc
At a later date, Saitama and Genos are watching, as Bang demonstrates one of his techniques to the duo. Upon being asked to attempt the technique, the pair express their disinterest in a non-destructive technique, eliciting an outburst from Bang's only disciple Charanko. After being questioned on the whereabouts of the rest of his students, Bang explains that a long time ago one of his students went out of control and defeated a good handful of the others causing most of them to leave the dojo; subsequently forcing Bang to take it upon himself to take him down. After hearing this story, Saitama remarks that Bang must be quite strong, evoking yet another outburst from Charanko. Shortly thereafter, a member of the Hero Association arrives and declares that all S-Class heroes are to report to Headquarters immediately to address a major crisis. Genos states that, since all S-Class are being convened, they might have need of Saitama's power and Saitama accompanies them to Headquarter.
The first S-Class hero to interact with Saitama is S-Class Rank 4 Atomic Samurai who, even after hearing the praise of Saitama from Bang, refuses to shake Saitama's hand; stating that he will only acknowledge those in the S-Class category. Saitama then hears a flurry of disapproving remarks at his presence at the meeting and looks over to discover the culprit is a very young girl who, to his surprise, happens to be the S-Class Rank 2 Tornado of Terror Tatsumaki. Thinking she's just some cheeky kid, Saitama blatantly ignores her and goes to sit down with the rest of the heroes, angering Tatsumaki, who is unable to do anything about it other than complain. As most of the S-Class heroes are conspiring with their own thoughts, Bang asks what they been called here for. Tatsumaki replies angrily that she doesn't know and they've kept her waiting for two hours. Saitama casually asks for some tea.
After having heard of the great calamity foretold by Shibabawa (who recently died due to choking on her own cough drops) Saitama found the opening to ask Puri-puri Prisoner who she was. The astounded S-Class hero enlightened him that this particular seer could predict a slew of 100% accurate and more than likely to occur disasters at exactly when and where they would and have most likely been to strike around the world, all in order for the Hero Association to prevent them from coming to pass. After hearing Sitch's panicked elaboration on how heavily the impact of the most recent prediction she'd made before her death would be come in half a years time, Saitama could not help but simply muse that this disaster that has the Association coordinator so on edge could just as well occur today or tomorrow for that matter. After having been asked who he was by the former, Saitama simply states how glad he is to have come along for the meeting.
Just then as he was finished bemusing over the emergency meeting, the entire building complex shook with thunderous turbulence as though it had been hit by a massive tremor, while outside the complex numerous Tengu like creatures led by the Sky King could be seen gathering around for an all out assault on the surface world. However, the would be incursion was soon dispatch by a UFO like albatross the size of a major metropolitan area. Having already picked up on what had happened to the obliterated A-City outside the Hero's Association HQ Saitama quickly leaped into action even before Genos could erect a response out of him, having already jumped all the way to the rooftop through every single floor of the super reinforced building to get a better view of the enemy at hand.
Upon seeing the spaceship, he headed towards it, evading and deflecting cannon fire directed at him. As soon as he managed to reach it, Groribas gets in his way, but was defeated in a single punch. He kept searching inside while wrecking whatever got in his way.Geryuganshoop tried to beg him into leaving the spaceship, but he did not listen. He eventually reached Boros, leader of the invading aliens. Before he could fight Boros, Geryuganshoop challenged him, but was easily dispatched; Saitama stating that flinging rocks around using telekinesis was a waste of superpowers before flinging one through the latter's head. Boros was amazed that he managed to defeat his strongest fighters as easily as he did and proceed to take him on.
As the battle of S-Class heroes and alien invaders began, Saitama's own battle with Boros was getting underway. After hearing why the aforementioned galactic warlord went on a tyraid, shattering planets and razing civilizations, all due to insurmountable boredom out of being an unstoppable force looking for an immovable object to temper his might, Saitama whacked him one but good on account of his disgust towards Boros's petty genocidal indulgence. Doing so however, inadvertently shattered his armor which acts as a restraining bolt on the intergalactic raiders own power. This somewhat surprised Saitama as this new opponent was one of the first individuals he's ever met to survive his one hit kill blow. Soon metamorphically shifting into a more powerfully energized form Boros begins releasing his unsealed inner power. As the two clash repeatedly Boros compliments Saitama on having lasted so long against his might while the latter retorts that his adversary is equally impressive.
As the continuous battle grows more and more intense Boros begins taking the upper hand in the conflict against Saitama, knocking him around his vessels throne room eventually culminating in the two plowing through to the top of the ship. There Saitama weathered some of Boros's strongest attacks only taking minimal damage in his assault. After having grown bored with Boros' constant boasting and flaunting of his regenerative capabilities, Saitama wonders aloud if he was finished due to his inability to fight seriously. Boros responds by unleashing his most powerful transformation yet, the "Meteoric Burst" then unleashing a thunderous onslaught which began wrecking his own ship, subsequently kicking Saitama all the way to the moon. Both incensed and excited about the intense battle to come and Saitama catapulted himself from the moons weaker orbit back to earth landing meteorically upon his adversaries ship, causing it to jolt towards the ground upon upheaval due to said impact. Meeting Boros' ferocious attack, Saitama simply countered with a devastating blow of his own, followed up soon after with a simple punch that promptly eviscerated his target only for him to quickly regenerate his scattered self back together.
Initiating his final measure the dreaded Boros struck out at his worthy opponent with his planet killing trump card intending to decimate Saitama and the earths surface layer in one gigantic blast. However, Saitama, unfazed by this apocalyptic announcement, simply said he would counter with his own winning trump card; his serious series, which not only deflected the genocide wave, which obliterated Boros on the spot, but also parted the cloud cover for several thousand miles across the globe. While he lay dying, admitting he found the excitement he long sought after while making his way across the cosmos, Boros commented that he and Saitama fought to the bitter end with neither giving an inch with the former nodding in compliance. Even though Boros knew full well that Saitama was still holding back the entire time they fought disparaging at how powerful his better truly was with his last breaths, leaving Saitama to solemnly walk away from his fallen enemy in the collapsing fortress.
After finally making his way out of the ruined spaceship, Saitama met with many other S-Class heroes such as Superalloy Darkshine, Tatsumaki and Atomic Samurai. After being asked how and why he was on the enemy ship, Genos came rushing to the scene concerned for his well being. After a brief conversation over who Saitama was fighting against and how prophesies could have come to pass without his help, which Saitama writes off as untrue, due to prophecies being untrustworthy, Tasumaki bursts into a fit of anger interrupting them both, denouncing Saitama for what she perceives as interference in her battle and calling him names. With some coaxing from Saitama, Genos steps up and tells Tatsumaki off, seconds before being telekinetically thrown into some debris by her in outrage of being called a brat only to be stopped seconds away from attacking Saitama by Bang who admonishes her for her callous behavior as an S-Class hero. After the invasion Saitama later destroyed Pluton with one punch and angrily yells in frustration.
Saitama and Genos are in M-City and see King's presence thanks to Genos, who gave a short description about him. Genos wonders why King was there. While they talked, a sudden commotion occurred, where the source is the robot G4, whose primary goal is to eliminate King in the order of The Organization. Though Saitama offered on helping, Genos declined in the hopes of making it to the top 10, making Saitama to leave the matter to Genos. While King struggled to choose a name in a video game, Saitama entered King's residence. At first, King didn't notice and told Saitama he'd die of shame when his hero name is used to refer to as "Onii-chan". Once King notices Saitama, Saitama states that the window was open, despite it being in the 22nd floor.
Eventually, King remembered Saitama from the S-Class meeting and quickly changes the video game to an action game, claiming he got the wrong game by mistake. As Genos fought G4, King played video games, which earned the praise from Saitama himself. However, Saitama suddenly addressed King's escape from a fight against the robot. Such questioning was garnered for Saitama wanted to relate to King's strength. As Saitama was going to exit, a bird-like monster appeared, flying directly towards King's room. Lucky for King, Saitama stopped the monster by holding its beak. Saitama gave King a chance to fight the monster. Saitama then wondered if King attracted monsters, making king to reminisce his past. It is then shown that King really was attracting monsters before, only to be stopped by a mysterious figure from time to time.
Because of his appearance in the scene, people began to treat him as the hero, giving him the hero name KING. As King was driven to the point where he teared up, silence entered the room, making him think the monster ate Saitama instead. However, Saitama began to notice that all rumors about King were mere lies, though that didn't make him angry. King concluded that Saitama beat the monster and he also learned that it was Saitama who saved King countless of times, albeit Saitama still had hair at the time. King began to apologize to Saitama and confessed that he stole the glory from Saitama's accomplishments. Still, Saitama urged King not to quit and just be strong. Saitama went away, holding no grudges against King, and he still wanted to play games with King.
Human Monster Saga
The Blizzard Group Arc
Fubuki, along with Eyelashes and Mountain Ape, goes to Saitama's place to convince him into joining their group. However, the latter's casual refusal urged them to take him down, but backfired as Saitama easily knocked out Eyelashes and Mountain Ape. She expresses her will to secure her position as the Rank 1 in B-Class and attacked Saitama with a psychic barrage, but Saitama is not surprised by her ability. Saitama withstood all of her attacks and even patronizes her about being a hero. She asserts her will and continued to attack, this time with a box cutter, but was caught up by the impact of Genos's attack on Speed-o'-Sound Sonic, who evaded it. Saitama quickly got between Blizzard and Geno's attack, which would have probably killed her.
Wondering about Genos's presence, she is more surprised that the S-Class hero actually called himself the disciple of the B-Class Saitama. Genos recognizes her, but misinterprets her position as being due to a failed attempt at taking down Saitama, when in actuality she was caught in his attack. Sonic then proceeds to attack Genos with exploding shurikens, but they did no damage. The two are on equal footing and eventually Saitama tries to stop them.
Upon observing Saitama's ability while battling Sonic, she found that Saitama is too strong, which is far from the norm for his Class ranking. It is revealed that she has an inferiority complex due to her sister's own power. Due to this, she founded the Blizzard Group in order to surpass her sister, who is a lone wolf. Still, she reveals that she does not want to advance to A-Class, due to the A-Class heroes being overwhelmingly powerful, such as the Disciples of Atomic Samurai and Sweet Mask. However, she acknowledges that she can get to upper ranks of A-Class.
In a final attempt to persuade Saitama in joining her faction, Fubuki belittled Saitama, saying he won't advance alone and that there are several other heroes out there that are stronger than he is. However, when King appears demanding Saitama return the video game he borrowed, Fubuki decides to follow him and be a part of his group, noting that the strong are attracted to Saitama, who does not discriminate on strength. Saitama is shortly after given the hero moniker "Caped Baldy" by the members of the Association.
Hero Hunt Arc
Saitama was seen playing video game with King, along with Fubuki and Genos, while being visited by Charanko, who wants know why his master, Bang, expelled him all the sudden. Genos tells Charanko that Bang expelled him because Garou was actively hunting heroes. Saitama does not remember who Charanko is and has to be reminded by Genos that Charanko is Bang's one and only disciple.
Saitama visits the heroes who were beaten by Garou, particularly Mumen Rider, Tanktop Master and Charanko, to give them some bananas as treats and to know more about Garou. He first visits Mumen Rider and Tanktop Master, where he wants to know about who exactly Garou is, instead of just being Bang's former disciple. Now knowing that Garou is a strong villain, he wishes to meet and battle him someday in person. Saitama later visits Charanko to learn more about martial arts and who he could fight to learn more about it. He is soon offered by Charanko to observe marial arts at the tournament called Super Fight that he was originally supposed to participate in but couldn't due to his injuries. Saitama accepts the offer, however, Charanko advises him not to do something like disguise himself to cover his identity in the tournament. Enticed by the 3 million prize for 1st place, Saitama intends to do exactly that.
After Saitama finds a wig shop, he is attacked by Garou. Garou, thinking that Saitama is after him, tries to attack him with a swift karate chop to the shoulder. However, Saitama is not only unaffected, but also fails to recognize his attacker. Annoyed at Garou for attacking him, Saitama counters Garou's attack by using a karate chop of his own which knocks out Garou almost instantly and then carries on buying a wig for his disguise. On the following day, Saitama prepares himself for the tournament by preparing the wig. Genos sees what Saitama is doing and, believing that Saitama is trying to make up for his lack of hair, decides to help his master by calling Dr. Kuseno and asking him to transplant the hair fibers onto Saitama. After getting the doctor to agree, he asks Saitama if he is free that day, at which point Saitama is finally able to explain that it is a disguise for the tournament, used to make himself look like Charanko. He then asks Genos to join him in paying them a visit, and to learn what martial arts is really about.
Monster Raid Arc
Saitama is in Charanko's waiting room looking over a list of the contestants of the tournament. He is then greeted by Sour Face, and Sour Face discusses a tournament incident that happened in the past and his reasons for joining the tournament. Lastly, he talks about the day when Garou rampaged through the dojo. Saitama implicitly states that what Sour Face is doing is pitiful and claims that he will be the one to put Garou down in the end, unaware that he had already beaten Garou before the tournament, which aggravates Sour Face.
After the tournament introductions, Saitama converses with Sour Face, when Zakos appears and starts questioning Saitama. Sour Face ends up answering some of Zakos questions. Zakos then reveals that Bang was supposed to be one of the judges and starts mocking the martial arts master. Sour Face starts to feel very insulted, but felt even angrier when "Charanko" did not seem angry at Zakos's comments. Saitama replies that he was not invested in the conversation and is only looking forward to fighting Zakos, but notes that Zakos doesn't seem strong.
Saitama asks Sour Face what a reverse seed is after Max's and Lin Lin's match. Zakos tells Saitama they're reverse seeds and Saitama inadvertently angers Zakos by calling him a weakling. In his fight against Zakos, he single handedly beats Zakos, which surprised the audience and brought the attention of Suiryu.
During Max's fight with Suiryu, everyone is impressed except Saitama and Bakuzan. Saitama prepares to fight Bakuzan after Sour Face's match. When Bakuzan walks up to Saitama, Saitama asks Bakuzan for a taste of Bakuzan's martial arts, which the martial artist fully accepts. However, as Bakuzan is demonstrating his martial arts to Saitama, he accidentally shifts Saitama's wig, causing Saitama to panic and launch Bakuzan into the air. He crashes into the floor, headfirst.
Saitama goes on to face Sour Face and defeats him in a manner similar to Bakuzan. Even landing him in a spot next to where Bakuzan was.
Super Fight Arc
Saitama is pitted against Choze in the semi-finals and defeats him, proceeding to the finals of the Super Fight. In the finals he fights against Suiryu. During the fight Suiryu uses strong kick that has enough force to knock off Saitama's wig. During the fight both express the struggle to fight strong opponents, to which Saitama agrees and asks Suiryu to give him the true experience of martial arts since he's starting to get tired of ending his fights with one punch. Suiryu agrees and asks for the same.
As their fight continues, Saitama managed to block some of Suiryu's kicks, until he was struck into the air and kicked back down and Suiryu landing on his face. Saitama came out unscathed, but tries to keep his wig on whiled blocking and dodging. Saitama was them dared to punch back, but Saitama backed away. When asked about his routine, he accidentally let it slip he beats monster and tries to mend it by stating he wants to join the Hero Association, but was blown off by Suiryu. After listening to Suiryu philosophy, Saitama wig came off when Suiryu kicks his head, Saitama replies back, telling Suiryu not to get any stronger if he wants to have fun before throwing a punch, stopping before Suiryu's face.
After the wig came off, Saitama was disqualified and Suiryu was declared a winner. However, Suiryu still continues to fight him and doesn't hold back. Suiryu uses multiple barrages of different attack, but Saitama is completely unfazed. After receiving all of Suiryu's attack, Saitama concluded that martial arts is just about moving in a cool way. He then tries to mimic Suiryu's attack, but accidentally launches him out of the arena. However, Suiryu is still chosen as the winner of the tournament, due to Saitama breaking the rules. The referees then try to catch Saitama who runs away.
Saitama later returns to the arena after hearing Suiryu's voice calling for help. The hero saves Sneck from Bakuzan, and commends Suiryu for holding his own against the monsters. He then proceeds to confront Bakuzan, telling Suiryu to leave the rest to him.
Suiryu is overwhelmed by Saitama's arrival. Bakuzan recognizes Saitama as the opponent who had defeated him in the tournament. The monster unleashes a flurry of blows on Saitama who is not at all affected. Saitama tries to recall Bakuzan but fails to do so. The hero punches Bakuzan, blowing off much of the latter's torso and killing him. Saitama then introduces himself to Suiryu.
Suiryu thanks Saitama and warns him of Gouketsu and the Monster Association invasion. Saitama decides to fight Gouketsu. Suiryu tries to prevent him but in vain. Moments later, Saitama kills Gouketsu with one punch and the latter's head flies and lands in front of Suiryu. Suiryu decides to become a hero after being inspired by Saitama. He asks Saitama to accept him as a disciple, but Saitama flatly refuses.
Saitama immediately leaves in search of other monsters, but is unable to find them. He finds out from C-Class hero Water Gun that the monsters attacked for 3-4 hours before retreating simultaneously. Saitama feels bad for being oblivious to such an emergency and reflects on himself. He questions the Monster Association's actions. Thinking of today's events, Saitama wonders if his boredom is being caused because he is forgetting something very important. It is also revealed that Saitama was interested in fighting Garou to overcome his boredom. In order to acquire experience in Martial Arts, he took part in the Super Fight Tournament. But despite fighting the best of the best martial artists, Saitama gained nothing insightful. The hero goes home after killing a random monster.
Monster Association Arc
On the way, Saitama meets King, who was on his way to buy manga. King and Saitama have a deep discussion on what it means to be a hero. Garou spots King and is about to attack when Saitama kicks him and sends Garou crashing into a wall. Both Saitama and King are unaware of Garou's appearance. Saitama hopes to meet the Hero Hunter who might give him a good fight.
He manages to put King on the ropes, (In a video game) but is still unable to defeat him, even with a two finger handicap. On his way to take out the trash, Saitama is attacked by several monsters but he disposes all of them without any trouble in a short amount of time. He begins to wonder if those monsters are looking for him. However, when he looks at the time, he then rushes to beat the garbage truck.
Saitama continues to play video games with King and as he was winning, King easily defeats Saitama, much to his frustration. Saitama noticed King's Emergency Transmitter has been beeping, and King notes that there is a monster nearby, but inform Saitama that an S-Class heroes is already at the scene. King then ask about Genos' whereabouts, to which Saitama states he doesn't know. Saitama was then informed about the Monster Association and decided to head over toward the monster, worrying about Genos' safety.
Saitama and King arrive in time to witness Elder Centipede as he's about to kill Bang, Bomb and Genos, fresh from fighting against Garou. King lures Elder Centipede in with promises of fighting against Blast, and Saitama annihilates the gigantic beast with one of his serious punches, something that after being soundly defeated by King in video games so many times, fills him with a rare sense of satisfaction. Genos, after witnessing Saitama's latest display of power, limps over to him asking what it is he's lacking, to which Saitama simply replies "power" much to the exasperation of King.
Saitama brings the wounded heroes back to his apartment to rest and plays a monster fighting game with King. Fubuki, arrives at the apartment and explains to the group the current state of alert of the Hero Association thanks to the Monster Association. Unfortunately, most of the group is still too badly injured after the fight against Garou and Elder Centipede and King predictably makes excuses and cops out.
Thus Saitama, growing increasingly annoyed with Garou, decides to put his costume back on and deal with him himself. Also he plans on picking up cabbage while he's out.
During his trip to find Garou, he eats at a restaurant where Garou also eats in at the same time but he seemly forgot to bring his wallet. As the result, he falls into deep panic and unable to call Genos for help since he is still busy fixing his body. Suddenly, Fubuki comes to offer her help to find Garou in exchange of 70% of the credit. Furthermore, she also propose to help him to stand at the top 5 in B-rank as she still believes Saitama cares about ranking. At the same time, what Fubuki doesn't know is that Saitama deliberately orders a large french fried dish to trick Fubuki to pay his meal.
As Garou commits dine-and-dash in the restaurant, Saitama grabs the opportunity to run and capture him, leaving Fubuki stuns because of his carefree reaction. When Saitama manages to catch up with Garou, he gives Garou the warning about eating-without-paying and leave the scene since Saitama is grateful for Garou for getting him out of the same circumstance. However, this enrages Garou as he thinks Saitama takes pity him and tries to hit Saitama. Unfortunately for Garou, Saitama knock outs Garou for the third time and run away.
|The following section contains Webcomic spoilers. You have been warned, manga-only readers.|
Following Bang and Bomb's disastrous attempt to capture Garou, Saitama ended up hosting a potluck in his apartment with them, Fubuki, Genos and King. Just when the food was done however the first four all made a grab for the food at once knocking King out in the process, scattering it all around Saitama's apartment before squabbling over what little remained.
During this little scrape everyone's cell phones are smashed, thus the group only learns about the 'Monster Raid' when King wakes back up and check's his messages. The group ends up splitting up as they investigate the underground passageways that are the Monster Association's base, Saitama, quickly getting separated from King, soon encounters Overgrown Rover and forces him to 'sit' with a punch to the face.
Afterwards Saitama continues to explore the base and meets up with Flashy Flash, and ends up impressing another S-Class Hero when he manages to easily outmaneuver his fastest attacks. Unfortunately the two end up getting trapped together when Tatsumaki rips the Monster association headquarters out of the ground and leaves it upside down.
Saitama subsequently spends the bulk of the night being ordered to use his brute strength to yank out various pieces of rubble in a very specific order in order to prevent the make shift cave from collapsing in on them. The two eventually make it to the surface where they witness the bulk of the upper echelons of the Monster Association fight the heroes.
Although Saitama wishes to join in Zombieman insists that he stay out of the fighting on account of the heroes pride being on the line. One by one the monsters fall until only the duo of Black Sperm and the newly born Golden Sperm remains. Then Garou, freshly turned into a monster, arrives on scene and effortlessly kills off Golden Sperm and severely wounds Black Sperm.
Garou announces his intentions to kill off a young child that the Monsters had taken hostage and dares the heroes to stop him, and one by one the heroes fall before the insanely powerful Monster. At this point Saitama makes his appearance known in spectacular manner by defeating Evil Natural Water in a single hit. The two do battle Saitama noting that like he himself usually does, Garou is not even fighting seriously.
As such in order to 'encourage' Garou Saitama uses his 'Serious Table Flip' to flip over the largest portion of the Monster Association headquarters catapulting Garou so high into the air that he loses track of which way is down where the two do battle once more before eventually landing on the makeshift mountain that is the upside down headquarters once again.
As the fight continues Garou's frustration causes him to continue to Monsterize, though as Saitama notes Garou is actually growing weaker, his later forms sacrificing the skill that was his forte for brute power. Eventually Garou himself realizes this as Saitama continues to beat him down before he finally explodes at Saitama in anger.
Garou begins to rant about how the Heroes can't save everyone, and what Humanity truly needs is an enemy to unite them against a common threat 'the Ultimate Monster' and demands to know the reason why Saitama is a hero and the source of his bottomless pit of strength. Saitama's answer of 'it's just for fun' however only causes Garou to break down emotionally and mentally.
Once Garou finally calms down Saitama realizes the real reason Garou fights; he wanted to be the hero that would save humanity, but once he realized he couldn't he instead decided to 'take the easy way out' and become a monster. In spite of the other heroes insistence, Saitama refuses to kill Garou on the grounds that he's still human.
Saitama goes so far as to prove this fact by shattering Garou's outer shell and revealing the very much human Garou underneath. Coupled with that, the child that Garou had supposedly tried to kill tearfully rushes onto the scene and reveals that Garou actually saved him from the Monsters, twice. Garou is eventually convinced to run away with none of the Heroes being able to stop him.
Psychic Sisters Arc
Saitama is formally promoted to A-Class rank 39 and in the process granting him a new much more luxurious apartment in A-City by the Heroes association. Over the next few days Saitama collects what remains of his belongings from the rubble of Z-City where he encounters and ends up unwittingly adopting the now much smaller Black Sperm and Overgrown Rover as pets.
Saitama makes his way back to A-City where he and his new would be pets are attacked by A-City's robotic security system. After being questioned by security on how the robots were destroyed Saitama is escorted back to his apartment by King. There Saitama plays host to his three 'seniors' in the apartment complex Butterfly DX, Chain'n'toad, and Forte.
Forte, after his musical fighting style is insulted by Saitama, challenges him to a fight and Saitama agrees on the condition that if he loses he has to take in the two former monsters that followed Saitama home. Saitama has his easiest victory yet when the Blizzard Group hits Forte with their car in the parking lot during their blind rush.
Entrusting the two formerly dangerous monsters to Butterfly DX and Chain'n'toad Saitama joins Fubuki as she makes her way into A-City's prison for monsters. Leaving her employees on the ground level Fubuki explains that they're going to see Psykos the leader of the now disbanded Monster Association. Apparently when she was in highschool with Fubuki Psykos developed the ability to see the future.
One day however Psykos saw something so horrible that it made her want to wipe out all of humanity, and now Fubuki wants to know what it is she saw. Unfortunately Tatsumaki arrives on scene intending to Kill Psykos for her earlier defeat and the two sisters end up in a clash of psychic powers over her life while Saitama fights the other monsters who are trying to escape in the ensuing riot.
After dealing with the monsters Saitama returns to ground level where he stops Tatsumaki from hurting Fubuki any further. The two soon clash Saitama taking the fight out into the desert that surrounds the city. Tatsumaki however is soon met with immense frustration when her telekinetic powers fail to rip Saitama apart, smash him to pieces or even stop him from calling her a midget.
The pair's fighting takes them all the way to H-City and back; along the way they are mistaken for a Dragon Class threat by the hero association, nearly crush a family that was moving into A-City, kill a dragon class monster that was destroying H-City without even realizing it and takes down an entire criminal gang without much effort.
Unfortunately for her Tatsumaki discovers that her already severe injuries from the monster raid have been further aggravated from fighting Saitama and the two of them decides to put the fight on hold for the time being. That said Tatsumaki thinks she has the last laugh after burying Saitama alive under several hundred feet of earth.
Later on during Tatsumaki's second confrontation with the Blizzard group that day Saitama digs himself out and interrupts another spat between the sisters. There, observing Tatsumaki's severe injuries, he points out to the Blizzard group that this is their one and only chance to make Tatsumaki leave them alone for good, to which they declare their intentions to get strong enough so that not even a Tatsumaki in full health can stop them.
As soon as Tatsumaki vacates the scene, Saitama shortly follows suit intercepting her to speak with her. Predictably she rebukes his approached denouncing him for hiding his true strength although Saitama speaks to the contrary, giving an eyeroll response to her boast that she could take him in five seconds if in perfect health.
Asking why she is in the Hero Association if she hates human contact so much, she insults him before going on to state her reasons only to retract it soon after flying off again, leaving him to wonder what the term "Bla-" means. Saitama is later seen in the Hero Association Headquarters, where he sees Forte, Butterfly DX, and Chain'n Toad. Saitama tells the three heroes to not come into his house without permission.
Surprisingly, Forte apologizes to Saitama for his rude behavior earlier. Seeing Saitama's current state, Forte offers his clothes and and shoes, which grosses Saitama out. It is revealed that Forte saw Saitama from the hospital room, fighting. He tells Butterfly DX and Chain'n Frog that they are no match for Saitama. The three heroes than decide to be accepted by Saitama.
Fall of the Hero Association
After Genos defeats the Forest King, he challenges Saitama to a duel, which he accepts. When they do fight though, all that Genos manages to do is temporarily blind Saitama before he stops, claiming that the best he could do is get Saitama dirty. Saitama admits that he can't tell if Genos has gotten stronger, only a lot brighter, which only further depresses him.
Genos comes to the realization that Saitama wasn't even remotely threatened by Genos's attack just now. Genos explains to Saitama that when he first agreed to take him on as a pupil Saitama told him to try to climb to the top of the Heroes Association, but that has gotten him nowhere. Genos also explains that the Heroes Association is dying.
At this point in time, the public's opinion of the association is that it takes their money to pay increasingly incompetent people who barely holds back the monster threat and usually cause as much, if not more, property damage than the monsters they fight. Another group, calling themselves the Neo Heroes has been created in response to this public outrage.
The Neo Heroes claim to have taken a look at the mistakes made by the Heroes Association and seek to correct and improve upon the formula, claiming to have two thousand possible candidates selected, including pro heroes from the Hero Association. Genos's question is, if Saitama thinks that they should transfer over the Neo Heroes, as he feels with a higher standard set, he might become stronger.
The subject changes over to why Genos is so obsessed with becoming stronger, with Saitama voicing a thought that had been bothering him for a while, that he could have simply killed the cyborg Genos has been hunting for the past five years. Genos admits that it's a possibility, but he's still preparing for the day that the bout finally comes before changing the subject back, and asking if Saitama wishes to transfer over to the Neo Heroes, to which Saitama says no, and to which Genos says he won't either. Arriving back at the headquarters the pair discover Forte as he finishes constructing a dog house for Black Sperm and Rover. Saitama introduces Forte as his neighbor and seeing as how Saitama doesn't wish to move out of his cramped little apartment and he can't move in with him, Genos takes Forte's Apartment.