ONE PUNCH MAN

A monster named Vaccine Man wreaks havoc in a city and is about to kill a young girl when a bald hero named Saitama intervenes and kills him with a single punch. Saitama recalls the events three years earlier that pushed him to become a hero; after saving a boy with a cleft-chin from Crablante, Saitama resolved to become a hero but became too powerful for his own satisfaction.

A cyborg named Genos tracks down a mutant called Mosquito Girl, whose mosquito swarm drains the blood out of everyone they come across within the city. Genos has a difficult time with Mosquito Girl. Saitama then suddenly stumbles into the fight, easily killing Mosquito Girl. Despite Genos's extremely boring explanation of his past, Saitama agrees to make Genos his apprentice.

Doctor Genus, the House of Evolution's founding leader, wants to study Saitama's power to replicate it. Saitama and Genos reach the House of Evolution's base, forcing Genus to release his strongest creation: the unstable Carnage Kabuto. After Kabuto effortlessly defeats Genos, Saitama is eager to fight him, but Kabuto cowers upon sensing Saitama's limitless power.

The hard-headed criminal Hammerhead forms the Paradisers terrorist cell to demand free goods for the unemployed, targeting local business magnate Zeniru using stolen enhancement suits. While they easily defeat bicycle hero Mumen Rider, Hammerhead's men are taken out by Zeniru's hired ninja Speed-o'-Sound Sonic.

Saitama and Genos pass an exam for the Hero Association, with Genos placing in S-Class while Saitama ends up in C-Class by breaking every record in the physical portion of the exam but doing very poorly in the non-physical sections. They then attend an orientation seminar by Snakebite Snek, who is annoyed that Saitama does not pay attention to him.

Saitama tries to come up with ideas for mentoring Genos, then rushes off to find a villain once learning that C-class heroes get dropped off the registry after a week of inactivity. Sonic demands to settle their alleged rivalry, but Saitama refuses.

Scientists and astronomers are busy studying the flight pattern of a meteorite that suddenly changed its trajectory-towards City Z, with all S-Class heroes deployed to intercept the meteor. Only Genos arrives on the scene, followed by an aged S-Class hero Bang. He tells Genos the meteor evacuation protocols have begun and that he should clear out.

The Seafolk Tribe declare war on humanity. Saitama easily kills an octopus-like monster while on his way home. Mumen Rider is late to the scene and sees only the deadbody of the creature, and hears the crowd talking about Saitama. Mumen looks Saitama up on the internet and finds that he is powerful, but opinions are divided on him. At the coast, several large Sea-Folk monsters emerge from the sea.

Genos initiates the battle and seemingly overpowers the Deep Sea King until the monster rips off one of his arms. He tells the civilians to flee before being badly damaged shielding a child from a glob of acid before Mumen Rider appears. Despite his determination and the civilians cheering him on, Mumen Rider is brutally beaten until he is caught by Saitama, who arrives in that exact moment.

The Ancient King of the Terror Lizard Clan appears but is easily destroyed by Tatsumaki. At Bang's dojo, Bang tells Saitama and Genos about how his former best student, Garou, had gone wild and defeated all of his other top students. Suddenly, a Hero Association member comes and informs the heroes that an emergency has been declared and all S Class heroes have been called to a meeting.

The Ancient King of the Terror Lizard Clan appears but is easily destroyed by Tatsumaki. At Bang's dojo, Bang tells Saitama and Genos about how his former best student, Garou, had gone wild and defeated all of his other top students. Suddenly, a Hero Association member comes and informs the heroes that an emergency has been declared and all S Class heroes have been called to a meeting.

Boros starts fighting Saitama, and their battle greatly damages the spaceship. Meanwhile, Mumen Rider, Stinger, and Lightning Max rescue the last City A survivors.