Saitama and Genos break into the House of Evolution's basement. There, they meet Dr. Genus and Carnage Kabuto. Genos attempts to defeat Carnage Kabuto, but is unsuccessful and mildly injured. Saitama then prepares to fight the monster.
Carnage Kabuto uses his immense speed to get behind Saitama and punch him, only to quickly retreat. Kabuto's instincts are sending him danger signals that are telling him he would've died very quickly. Kabuto asks him how he got so strong, with Saitama claiming that he did 100 push-ups, 100 sit-ups, 100 squats, and a 10 km run every day for 3 years.
Genos and Kabuto don't believe him and Kabuto starts to transform into Carnage Mode. In this mode, Kabuto goes on an uncontrollable berserk rage for a whole week that he claims is unstoppable. The room changes from white to red and Kabuto states that he will go on a rampage until next Saturday, which utterly surprises Saitama.
He starts to rampage and fling Saitama around the room, seemingly like a ragdoll. As he does this, Saitama starts pondering about what the rampage going until the next week could mean for him. He admits that he has made a horrible mistake and realizes that it is also Saturday today. With horror, Saitama loudly announces that it is a bargain day at the supermarket whilst one punching Carnage Kabuto. The room turns back to white and Dr. Genus stands awestruck.
Saitama states that he screwed up and Genos tells Dr. Genus why Saitama is upset. Genos shows a picture of the bargain at the supermarket, revealing it happens Saturday only. Genos tells Saitama that they could still make it to the supermarket if they hurry. Dr. Genus says that he is done with evolution and that he needs to make a change. Saitama and Genos blast a massive hole through the wall of the combat experimentation room.
- The battle lasted 1 minute and 13 seconds.