Chapter 1

"One Punch" (一撃, Ichigeki) is the 1st chapter of the One-Punch Man manga series.

Summary
A quiet and peaceful A-City is suddenly disturbed by an enormous blast that obliterates the surrounding area. Standing in the crater the blast left behind, is Vaccine Man. He slowly takes flight, powers up and fires multiple blasts at the city below. The energy blasts destroy the buildings and kill a large number of civilians. Meanwhile, Saitama is at home and watches the news, where the destruction and mayhem are being reported live. Saitama decides to stop it.

Near Vaccine Man, a schoolgirl is seen crying for her parents. Vaccine Man approaches her and seems to lend her a hand, but the hand suddenly transforms into a monstrous claw and reaches for the girl. Luckily, she is saved by an incoming Saitama, who grabs the girl and dashes away from the monster. Vaccine Man asks for Saitama to identify himself and he does, by saying that he's just an average man acting as an average hero. The creature is angered by this and aggressively tells the tale of who he is and where he came from. He transforms into a much larger and much more vicious version of himself and looms over Saitama. Saitama however, is completely unfazed and throws a punch, instantly blowing a hole in the monster, killing it. Realizing that the fight ended with one punch again, Saitama yells in frustration.