The Obsessive Scientist

A narrator opens the episode with the rise and fall of Dr. Genus, a gifted researcher who once dreamed of steering human evolution by hand. Growing bitter toward a world he judged flawed, he cracked the riddle of eternal life and populated his lab with copies of himself.

Bored by the lecture, Saitama cuts in, and Armored Gorilla explains that the scientist covets his body for study. Saitama first mistakes the interest for romantic attraction until Genos spells out that Genus wants him as test material. With a supermarket sale looming, the pair resolve to wrap things up quickly. Genos slips in a question about cyborgs that leveled towns four years earlier, but Armored Gorilla claims to know nothing.

Bracing for Saitama, the House of Evolution rigs its halls with hazards and grudgingly frees its ultimate creation, Carnage Kabuto. Genos flattens the surface complex with one energy blast and descends underground, where Carnage Kabuto trades blows with him without taking a scratch.

When Saitama steps up, the beast freezes, unnerved by the raw power it senses. Saitama casually credits his strength to a plain daily regimen of a hundred push-ups, a hundred sit-ups, a hundred squats, and a ten-kilometer run, a claim Genos refuses to accept. Carnage Kabuto shifts into Carnage Mode and briefly looks dominant, yet Saitama is simply distracted, having just realized the discount day is today rather than tomorrow. One punch ends the monster, and the two heroes leave to salvage what remains of the sale. Watching it all, Genus abandons his pursuit of artificial evolution, concluding that the person who truly needs to change is himself.

The adaptation fills in details the manga left off the page. The anime names each themed trap floor of the compound, running from maze, water, fire, blizzard, and electricity rooms up through needle, vacuum, and gravity chambers. Genos' assault is rechoreographed so that he kicks and circles Carnage Kabuto while spraying fire before his rapid strikes, and the monster retreats on beetle wings rather than leaping away. Several beats are anime additions, including the closing exchange between Genos and Genus and a Hero Association crew arriving afterward to survey the crater and marvel at Genos' firepower.

Carnage Kabuto delivers the post-credits monologue. A continuity quirk also stands out: a sunset glows through the hole Saitama smashes despite the room sitting underground, matching Genos' earlier remark that the sale runs until ten at night with roughly four hours left.