A single man arose to face the evil threatening humankind!
His name was Saitama. He became a hero for fun.
Together with his pupil Genos, Saitama continues making modest contributions as a Class C hero. With one punch, he destroys a massive meteor headed for Earth, but no one believes he could be so extraordinarily strong.
Next, the Deep Sea King-leader of the Clan of the Seafolk-attacks! Saitama and Genos race to confront the Demon-level crisis of unprecedented proportions!! The Deep Sea King wanders around destroying the city. In order to save the men he loves, the Class S hero Puri-Puri Prisoner squares off against the fierce opponent who has easily defeated even Class A heroes!!