Saitama Introduction Arc

The very first arc of the series and the launch of the Introduction Saga, this chapter establishes its central figure and the running joke that defines him. Saitama fights purely for the fun of it, yet his strength is so absurd that nearly every enemy falls to one punch, and that ease has drained the thrill out of heroism for him.

The story opens as a Dragon-level threat, Vaccine Man, lays waste to a city while Saitama watches on television and decides to act. Reaching the scene just before the monster can kill a child, he announces that he plays hero as a hobby. Vaccine Man transforms and squares up, only to be flattened by a single strike, leaving Saitama slumped and dismayed at how little the fight demanded of him.

A flashback recalls his run-in with the monster Crablante, who was chasing a boy that had scrawled on its shell. Saitama killed the creature to save the child, and the encounter set him on the path to training as a hero. In the present, his grocery run is broken up by the rampaging Brain and Brawn Brothers, whom he swiftly beats, though the blow levels much of B-City by accident.

Back at his apartment, Saitama is jumped by the Subterraneans in what feels like his first genuine challenge in three years, until it turns out to be a dream. When the real invaders surface, he instantly slays their king, and the rest withdraw underground.

The arc formally introduces Saitama alongside the frustration born of his overwhelming might. Two cities are wrecked between Marugori's assault and Saitama's own carelessness. A later arc reveals that credit for defeating Vaccine Man was handed to King, who merely happened to be present. It also emerges that the boy saved from Crablante was the grandson of the wealthy Agoni, whose response to the incident was to found the Hero Association.