One-Punch Man Wiki

"The Modern Ninja" is the fourth episode of the One-Punch Man anime series.


A man named Hammerhead is out to make a utopia of the overworked and underpaid model of modern society. Nobody pays attention to him on the street though, as he announces plans against the rich man Zeniru, who owns a nearby apartment building.

Saitama shocked after hearing the news

Elsewhere, Saitama appears to be having a nightmare about playing "rock, paper, scissors" with someone who has a booger on their finger. Suddenly, he is angered to find out that Hammerhead has made it so that having a bald head makes you dangerous. He runs out to put an end to it.

Meanwhile, Zeniru hires his own bodyguard to protect him against the movements of Hammerhead and his gang. His body guard is named Speed-o'-Sound Sonic. He faces the bald group on their way to Zeniru's lair and warns them that nobody usually survives after facing him in a fight.

In just a few seconds, Sonic beheads just about all of the Hammerhead bald group. Elsewhere, Saitama is getting called a terrorist for his bald head. Finally, only Sonic and Hammerhead remain. Hammerhead manages to escape with his life, but then runs into Saitama in the forest.

Hammerhead prepares to fight him by powering up. Saitama punches his entire suit off, seemingly feeling sympathy for him. Hammerhead runs away naked. Then Sonic shows up and tries to attack him, but Saitama explains that he's not one of Hammerhead's followers.

Sonic barely standing

But now that Saitama has blocked his attacks, Sonic still feels he must beat him. Saitama accidentally punches him in the crotch. Sonic then declares that he will train until he can beat him, while he barely stands from that one punch.

Back at home, Saitama tells Genos to leave him alone as he has a serious problem to solve. The problem is: nobody has any idea who Saitama is despite all of his accomplishments. Genos tells him to sign up on the official Hero Register online. Saitama and Genos register together, and must take a hero test to be official heroes.

Characters in Order of Appearance[]

Manga and Anime Differences[]

  • Mumen Rider getting the balloon is an anime original scene.
  • In the anime, there was a delay between Hammerhead putting his guard up and Sonic cutting his arm. In the manga, it seemed like Hammerhead just barely guarded in time.
  • King did not appear in the anime when Hammerhead destroyed the golden feces. Instead, it was paired with Saitama being mistaking by civilians as a Paradiser.
  • In the anime, Sonic did not wonder why Hammerhead was provoking him before realizing his plan.
  • Genos' scene with Dr. Kuseno is anime original.
  • In the manga, Saitama breaks Sonic's sword before telling him he's mistaken about him. It's the reverse in the anime.
  • Sonic does not mention anything about being faster than the speed of sound in the manga.
  • When Saitama is talking about all the monsters he has beaten, some from the bonus chapters make a cameo: 170,000-Year-Old Cicada Nymph, Personification Of A Light Pull Cord, and Octopus Claw Man.
  • Saitama and Genos going on the Hero Association website is anime original. In the manga, a summary of the Hero Association is given by Genos.
  • It is not mentioned in the anime that the HA was founded 3 years ago by Agoni at this time.
  • The Organization robot's scene comes after Sonic first meets Saitama and is still daytime, in the manga. In the anime, this scene comes after Saitama and Genos plan to take the Hero exam and is at night.
  • Saitama's scene after this where he thinks that he could have ended up like Hammerhead if he took one wrong turn in life is anime original. In the manga, Saitama contemplated this immediately after beating Hammerhead.


  • King again makes a cameo at the beginning of the episode watching the Paradisers address the public.
  • Hammerhead gives the episode monologue at the end of the credits.


Season 1 Episodes 123456789101112
Season 2 Episodes 123456789101112
Paradise Group Arc
Manga Chapters 12131415
Manga Volumes
Webcomic Chapters 12 • 13 • 14 • 15
Fights Speed-o'-Sound Sonic vs. Paradise Group and HammerheadSaitama vs. HammerheadSaitama vs. Speed-o'-Sound Sonic