Episode 13

"The Return of the Hero" is the thirteenth episode of the One-Punch Man anime series and the first episode of its second season.

Summary
Saitama and Genos are returning from the grocery store when they spot King, S Class Hero Rank 7. Tongue Stretcher terrorizes the populace but immediately surrenders when confronting King due to hearing King's Engine. A robot named G4 soon challenges King to a fight, but lets King leave with his excuse of going to the bathroom so they can fight at "full power". However, G4 will start murdering innocent civilians nearby if King doesn’t return in ten minutes. King panics because he isn't the "strongest human alive", but a normal ordinary Otaku who happened to be at the right place at the right time where monsters were destroyed and was given the credit, which he started accepting to become popular. When King sees Genos fighting G4, King runs away to his house to play his video game, Heartbeart Hottie Sisters 2. Saitama follows him and King is embarrassed to be caught playing a dating sim and switches to another game. Saitama plays video games with King, much to King's chagrin. Giant Crow attacks King's apartment, and in a state of panic King wets his pants and exposes his deception. Saitama kills the bird monster, which makes King realize it was Saitama who had saved him from the monster, Octopus Claw Man, that gave him the scar on his left eye long ago. Afterwards, Saitama plays video games with King while Genos gets upgrades from G4's equipment from Dr. Kuseno after defeating the robot. Sitch announces that he will be recruiting criminals to battle monsters due to the increased rate of monster appearances and the impending prophecy from Shibabawa. With heroes stretched thin, the Hero Association is willing to Speed-o'-Sound Sonic leaves the meeting after discovering Saitama was not present, as he only attended the meeting to fight him. In Z-City, Fubuki is discussing Saitama's unusual strength and rise in ranks with Eyelashes and Mountain Ape. They head out to look for Saitama. Saitama continues playing video games with King and is visibly annoyed at King hogging all the items to the point of accidentally destroying his controller. In the post credit scene, a man named Garou proclaims that this will be a slaughter party after reading the paper.