In a city plagued with thugs, mutants, and supervillains, Saitama decides to become a superhero for fun. He envisions an exciting life where he is constantly challenged with tough opponents, but after three years of intense training, he’s become so strong that he defeats every enemy with one punch! His dream of engaging challenging foes has gone up in smoke, and his overpowered life is filled with overpowering boredom. Then a cyborg named Genos learns about Saitama’s amazing ability and begs him to make him his disciple. Saitama isn’t interested in taking on an apprentice, but Genos isn’t giving up. Can he convince the disillusioned hero to teach him the secret of his strength? And will Saitama ever find a worthy adversary to battle?