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"The Obsessive Scientist" is the third episode of the One-Punch Man anime series.


The narration describes the story of Dr. Genus, a brilliant young scientist with ideas of artificially evolving humanity who became disillusioned with the world, eventually discovering the secret to immortality and creating multiple clones of himself.

Dr. Genus in his youth

Saitama cuts off the narration in his impatience and Armored Gorilla then explains that Doctor Genus is interested in Saitama's constitution (or as he puts it, his body). Saitama gets the wrong idea, believing the scientist to be homosexual until Genos explains that Genus wants Saitama for his experiments. The cyborg and Saitama decide to attack immediately, since the store discount day is the next day. Before they leave, Genos asks Armored Gorilla about any cyborgs active four years ago that have destroyed any towns, which Armored Gorilla denies. In preparation for Saitama's arrival, the House of Evolution sets traps in their facility and reluctantly decides to release Carnage Kabuto. Once they arrive, Genos destroys the above ground facility with a single blast before heading underground. The released Carnage Kabuto fights with Genos, taking no damage in the process. Carnage Kabuto then faces off against Saitama, but backs off when he detects how powerful Saitama really is. Saitama then reveals to the room his somewhat mundane daily training regime of 100 push-ups, 100 sit-ups, 100 squats and 10 km of running, much to Genos' disbelief.

Carnage Kabuto defeated

Carnage Kabuto unleashes his Carnage Mode and appears to be beating Saitama back, but it transpires that Saitama was just shocked by the realization that the store discount day was that day instead of the next and defeats Carnage Kabuto easily, leaving soon after with Genos to catch the rest of the discount day. Having witnessed this, Doctor Genus abandons his plans of artificial evolution, and realizes that he is the one who must change. After the credits, officials from the Hero Association inspect the House of Evolution blast site and discuss Genos' destructive power.

Characters in Order of Appearance[]

Manga and Anime Differences[]

  • Armored Gorilla didn't explain that the motivation behind Genus' plans was the pain/hatred he felt from the imperfection of humans. This monologue is done by Genus later when he goes to watch Carnage Kabuto fight Saitama.
  • Genos did not mention the rumors he's heard about the House of Evolution in the anime.
  • The dismembered bodies of Genus' clones were not shown in the anime.
  • In the anime Genus seemed more desperate when asking Carnage Kabuto to get Saitama's body than it appeared in the manga.
  • In the anime, Genos did not mention that many lifeforms he sensed in the base were the same, or guess that they were clones.
  • In the anime, Genos charged at Carnage Kabuto and kicked him, then circled him while blasting fire at him before doing Machine Gun Blows. In the manga, Genos sprinted right at Carnage Kabuto to use Machine Gun Blows.
  • Carnage Kabuto jumped back from Saitama in the manga. He flew back with beetle wings in the anime.
  • Genus did not introduce himself to Saitama before he explained how he got this strong, in the manga.
  • Carnage Kabuto still has a shocked/nervous expression when thinking "what kind of training" in the anime. In the manga, his expression is much more serious and focused.
  • Canage Kabuto vs. Saitama is extended in the anime.
  • In the manga, Genos never talked to Genus afterwards, Saitama and Genos didn't leave to try to make it to the sale in time, and Genus' very shocked expression was right after Carnage Kabuto got beat.
  • The Hero Association was never shown to check the destroyed House of Evolution base in the manga.


  • Carnage Kabuto gives the post-credits episode monologue.
  • When Saitama punches a hole to escape the combat experimentation room we see a sunset, even though they should be underground.
    • Genos tells Saitama that the sale goes until 10:00 PM, that they are about 4 hours away and if they hurry they can make it. This, along with the sunset, adds up as according to Genos, it is around sunset time right after Carnage Kabuto's defeat.


Season 1 Episodes 123456789101112
Season 2 Episodes 123456789101112
House of Evolution Arc
Manga Chapters 567891011
Manga Volumes
Webcomic Chapters 5 • 6 • 7 • 8 • 9 • 10 • 11
Fights Saitama vs. MosquitoGenos vs. Mosquito GirlSaitama vs. House of EvolutionGenos vs. Armored GorillaGenos vs. Carnage KabutoSaitama vs. Carnage Kabuto