Iaian (イアイアン, Iaian; Viz: Iairon) is the A-Class Rank 2 professional hero and a top disciple of Atomic Samurai.



Iaian without his helmet

Iaian is a young man with short blonde hair and blue eyes. He wears a long sleeved black shirt under his sleeveless medieval silver armor as well as a helmet. He carries his sword on the left side of his hip. After his fight with Melzargard, he lost his left forearm.


Iaian is shown to be quick-tempered as witnessing the widespread destruction of A-City, an act he deems "unforgivable," enrages him. Also, upon being attacked by a mysterious alien, Iaian gives no quarter and responds immediately with an attack of his own. He is quite headstrong and cocky since he willing to take on Garou head on to make his master proud of him without regarding his strength, although this could also be interpreted as a deep desire to make his master proud of him.

Iaian is described to be persistent in battle, refusing to back down regardless whether his enemy is more skilled.[1]


Webcomic notice The following section contains Webcomic spoilers. You have been warned, manga-only readers.

As a disciple of Kamikaze, Iaian was recruited after an apple cutting test. As Kamikaze has the ability to tell how a person lived their life by cutting with a sword, he only recruits disciples if they pass his test. At some point in the past he and his teammates fought Child Emperor and lost.


Hero Association SagaEdit

Alien Conquerors ArcEdit


Iaian dodging an attack and losing his arm

After the destruction of A-City, Iaian climbs out of the rubble only to see nothing standing in front of him but the Hero Association's Headquarters. He later saves a father and his son from being killed by Melzargard after the father moves some rubble to get to his son.[2] As he is standing there, the monster appears behind him and attempts to crush his head. Melzargard only crushes his helmet, its occupant having moved away in time. He states that there was no way he would not have noticed its killing intent and proceeds to attack the monster.[3] While dodging one of the monsters attacks, his left arm was torn off. Melzargard began splitting itself into five different form, [4] feeling hopeless of his situation, the monster is suddenly cut to pieces by Atomic Samurai and was ordered to stop bleeding by his master. [5]


Iaian surprised to see Silver Fang alive

While the S-Class heroes are fighting the monster, Iaian advises to retreat and find another way to kill the monster, but his pleas were futile.[6] During the fight he witnessed Silver Fang being struck by Melzargard attack and was surprised to see he was unharmed.[7] After the monster was defeated the spaceship that was above them began to collapse and Iaian was helped carried by Atomic Samurai.[8]

Human Monster SagaEdit

Super Fight ArcEdit

Iaian, Okamaitachi and Bushidrill are waiting outside discussing about Garou's hero hunt, while their master Atomic Samurai is attending a meeting with the Council of Swordmasters.[9] After Atomic Samurai killed the monsterized Haragiri, Iaian noticed the smell of blood and Atomic Samurai ordered they will strike the Monster Association.[10]

Monster Association Arc Edit

Iaian is seen waiting for the S-Class meeting to end with his fellow disciples.[11]

Iaian deflects Rhino Wrestler's attack

Iaian deflects Rhino Wrestler's attack

Iaian is one of the heroes who fights the first wave of monsters from the Monster Association.[12] When Rhino Wrestler appears from the 2nd wave, Iaian watches the other heroes attempt to attack the monster but fail miserably.

The A-class hero unsheathes his sword and strikes his horn, momentarily halting the monster's movement.

Iaian and Rhino Wrestler clash

Iaian and Rhino Wrestler clash

Rhino Wrestler rates his attack 69 points, and the other see it as the opportune moment to strike together. First, Jet Nice Guy attacks with his Ultimate Jet Straight across the monster's face; next, Double Fall tickles his nose to activate his energy sneeze. Crescent Eyebroll uses his Crescent Consecutive Slashes, while Narcisstoic uses his Rose American Sack attack, and the rest of the heroes join in, but Rhino Wrestler is able to blow all of them away, rating each of their attacks. The heroes are shocked at his power, while Rhino Wrestler reminisces of a moment when Gyoro Gyoro conversed with Rhino Wrestler before the monster raid and how Gyoro Gyoro commended the monster for the increase in strength. Rhino Wrestler screams out for the strongest heroes to fight him, all-the-while fighting Iaian. Rhino Wrestler is able to hold Iaian back, but before the battle could continue further, Atomic Samurai tells his disciple he would take his place. Iaian insists he could handle it, but Atomic Samurai tells him he would cut off his horn himself.

Webcomic notice The following section contains Webcomic spoilers. You have been warned, manga-only readers.

They assist their master and fellow disciples in the raid on the Monster Association HQ. They encounter Devil Long Hair, and Okamaitachi becomes infatuated with him. While Iaian and Bushidrill discuss a plan of tactics, they realize Okamaitachi is distracted and defeats him with the help of their fellow disciples. Iaian tells Okamaitachi to snap out of it, reminding them that this is the first mission in which Atomic Samurai allowed them to act on their own. Okamaitachi attacks with her Air Blade attack, but Devil Long Hair stops it with his hair, shocking the swordsmen. Devil Long Hair counterattacks, stabbing Okamaitachi through the chest.  The demon-level monster then extends his hair toward Iaian and Bushidrill, and the swordsmen prepare for battle. The three swordsmen work as a unit, rushing in and cutting Devil Long Hair's hair as fast and as effectively as possible, and manage to defeat him, although they admit it was a difficult opponent, and had they not worked together, they surely would have lost. But Okamaitachi, Iaian, and Bushidrill are attacked by Evil Natural Water, a Dragon-level monster, who defeats all of them and badly injures them, knocking Okamaitachi and Bushidrill unconscious. Child Emperor comes across them, and Iaian, the only one who is still conscious, urges Child Emperor to leave, as the monster is still lurking around. 

The three swordsmen are then swallowed up by Pig God, who found them and consumed them, and manages to bring all three of them up to the surface and regurgitate them without any noticeable injuries. As Atomic Samurai watches the other S-class heroes fighting and being unable to do anything since he lost his sword, Iaian speaks to his master and gives him his sword to fight Garou. 

Appearances in Other MediaEdit


The Murder Case That Is Too ImpossibleEdit

Heroes in spring

Iaian in the hot spring

Iaian was invited along with the S-Class heroes to a hot spring resort, after the Dark Matter Thieves failed invasion. While enjoying himself at the hot spring, he wasn't satisfied that some of the heroes that did not participate in the battle were invited to the resort, but Bang managed to calm down the situation. The next day after the ceremony, the heroes find Zombieman murdered, stabbed in the back by Atomic Samurai's katana.

Atomic Samurai alibi

Iaian at the banquet with the other heroes

As Child Emperor interrogates every hero, Iaian was one of many alibis for Atomic Samurai so all suspicions were dropped. While the investigation wasn't progressing, Tatsumaki tried to restrain everyone, until Zombieman suddenly woke up. Zombieman later revealed that Atomic Samurai's katana was floating with green light surrounding it similar to Tatsumaki, when it stabbed him. Zombieman didn't care about what happened the night prior and the heroes disbanded.[13]

Abilities and PowersEdit

Being the second highest A-Class hero, Iaian is a rather powerful individual. It is also stated by Fubuki that, like his fellow disciples, he could be S-Class if it wasn't for Sweet Mask. It is worth noting that while he was weakened after losing his arm, he still remains a powerful fighter.

Physical AbilitiesEdit

Enhanced Speed and Reflexes: Iaian is shown to possess outstanding speed and reaction time as he was able narrowly avoid a sneak from Melzargard from behind along with dealing a counterattack simultaneously. He also dodged a follow up attack from the alien at close range though not completely as he lost his left forearm from it. He is also capable of performing several slashes within a second.[1]

Enhanced Endurance: Iaian is very durable with high pain tolerance as he only displayed shock with no signs of outward pain from having his left forearm blasted off from Melzargard's attack.

Enhanced Strength Iaian was strong enough to stop charge from Rhino Wrestler, a Demon level monster. That is something that even a group of A and B class heroes were not able to do. Rhino Wrestler even acknowledged the strike to his horn, rating it a 69/100, which is much higher than what he rated the other heroes' attacks.

Fighting StyleEdit

Expert Swordsman: Being the top disciple of Atomic Samurai, Iaian is extremely skilled with the sword. He has been shown to have a rather keen grasp of what is happening around him, easily avoiding an attack from a large monster and then returning a strike right after.

  • Iai of Certain Kill (必殺の居合, Hissatsu no Iai): True to his name, Iaian attacks with iai strikes, unsheathing his sword, performing slashing attacks, and returning the sword to his sheath all in an instant. Each slash aims for the enemy's vitals and can be performed all under a second. Among the three disciples of Atomic Samauri, Iaian has the fastest swordplay.[1]


Katana: Iaian carries a katana that has a black hilt with a circular hand-guard. The sheath is painted black.

Knight Armor: Despite studying swordsmanship under Atomic Samurai, he dons a silver knight-like armor instead. During the invasion of the Dark Matter Thieves, the helmet was crushed by Melzargard's sneak attack. His armor is made by a famous blacksmith.[1]

Hero RatingEdit

Iaian's rating determined by the Hero Association:[1]

Ability Type Stamina Intelligence Justice Endurance Power Popularity Effectiveness Fighting Ability Total

Major BattlesEdit

Participants Chapter(s) Episode(s) Result
Iaian vs. Melzargard Chapter 31, 32 10 Interrupted by Atomic Samurai
Heroes vs. Rhino Wrestler Chapter 94 None Interrupted by Atomic Samurai
Webcomic notice The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Participants Chapter(s) Episode(s) Result
Iaian, Okamaitachi and Bushidrill vs. Devil Long Hair None None Win
Iaian, Okamaitachi and Bushidrill vs. Evil Natural Water None None Loss


  • Iaian's name is a Japanese portmanteau of "iai", a sword-based Japanese martial art, and "aian" or iron, referring to his armored appearance.
  • Iaian without armor.[14]
  • According to the databook:
    • What he likes are his master, his blacksmith, his favorite armor shop, and watermelon.[1]
    • What he dislikes are people who put a damper on conversations, demonstrating iai on TV.[1]
    • His hobbies are choosing swords, travel, golf, and visiting temples and shrines.[1]
  • The origin of his hero name comes from his unrivaled skill at Iaido (居合) and his iron armor.[1]


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 One-Punch Man Encyclopedia; One-Punch Man: Hero Perfection, page 28-29
  2. One-Punch Man Anime; Episode 10
  3. One-Punch Man Manga; Chapter 31, page 7-12
  4. One-Punch Man Manga; Chapter 31, page 22-27
  5. One-Punch Man Manga; Chapter 32, page 2-7
  6. One-Punch Man Manga; Chapter 33, page 3-4
  7. One-Punch Man Manga; Chapter 34, page 11-16
  8. One-Punch Man Manga; Chapter 36, page 3-4
  9. One-Punch Man Manga; Chapter 69, page 2-6
  10. One-Punch Man Manga; Chapter 69, page 25-27
  11. One-Punch Man Manga; Chapter 93
  12. One-Punch Man Manga; Chapter 94
  13. One-Punch Man OVA; The Murder Case That Is Too Impossible