"Because It's Raining" (雨降ってるから, Ame Futsu Terukara) is the 27th chapter of the One-Punch Man manga series.
Saitama stands between the unconscious Mumen Rider and the Deep Sea King as the citizens in the shelter look on. The citizens are worried because Saitama is only a C-Class and doubt his ability to do anything against the Sea King. Sea King introduces himself to Saitama, declaring himself to be the ruler of the sea and states that he stands at the top of the pyramids of all living things. Saitama then blows off Sea King's boasts and asks him to hurry up. Sea King, enraged, throws a punch at Saitama. Saitama returns with his own punch, which blows a hole through the Sea King's torso. The citizens look on in awe and confusion as the Sea King falls to the ground. The citizens then go into a frenzy of disbelief, stating how powerful Saitama is, until one citizen, in particular, starts causing trouble. He states that the Mysterious Being probably was not all that strong and that even if he was that the other heroes had weakened the Sea King before Saitama arrived. He then starts taking jabs at the heroes, stating that they were useless and weak.
Hearing this, Saitama begins to laugh and proclaims his luck that the other heroes had been there to weaken the beast and that he'd managed to take all the credit. He then turns to the citizens and tells them that they'd better tell everyone that he'd beaten it and that they better not snitch on him. The citizens then start talking amongst themselves, saying how the other Heroes had helped and that Saitama is just a cheater. Saitama makes one more jab at himself which causes the citizens to give their gratitude to the wounded heroes who had fought the beast rather than Saitama. Genos worries about Saitama position as a hero and declares if Saitama was in a tight spot, he will be by his side. Speed-o'-Sound Sonic returns equipped to the battle scene to fight the Sea King, unaware that the monster was defeated. The scene shifts to G-City, where the great oracle Shibabawa predicts a great catastrophe, the greatest of the era and states that the Earth itself is in danger.