Episode 3

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

Summary
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. 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 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.

Trivia

 * 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.