Episode 18

"The Monster Uprising" is the eighteenth episode of the One-Punch Man anime series and sixth episode of season two.

Summary
Lightning Max loses his fight with Suiryu, while Genos gets a message concerning a lot of monsters around the city. Sneck beats his opponent Benpatsu as the announcers receive alerts about monsters and plan on evacuating the audience, but Bakuzan convinces them not to. Sour Face beats his opponent Jakumen, but they part on good terms. Sourface excitedly tells Saitama that he won, but Saitama had gone to the bathroom. When Saitama faces off against Bakuzan, Bakuzan sadistically describes how he will destroy Saitama, but when Bakuzan touches Saitama's wig, Saitama comically punches him out of the tournament in one hit. Genos manages to kill all but one of the monsters, the Demon-level Awakened Cockroach, whom barely escaped. While Genos's back was turned, he is suddenly attacked by a mysterious being. Some of the Hero Association members find Pineapple and Mohican, and they learn that Waganma was captured, but not Narinki.

Meanwhile, Do-S successfully manages to brainwash all of Fubuki's henchmen, but Fubuki repels them back. Do-S asserts she's attacking Fubuki so that she can face Tatsumaki, but Fubuki tells her that whenever she's hurt, Tatsumaki will know. Right on cue, a monster lands in front of Do-S, with Tatsumaki arriving. Do-S orders Fubuki's mind controlled henchmen to attack Tatsumaki while she flees, but Tatsumaki easily knocks the henchmen into buildings. Tatsumaki lectures Fubuki that surrounding yourself with henchmen will cause you to become weak before flying away. When Suiryu and Sneck face off, Suiryu casually avoids Sneck's strikes. He taunts Sneck by telling him that he is ineffectual as a hero, and that he sought power with no particular agenda. Suiryu's nonchalant attitude enrages Sneck, but Suiryu knocks him out with a single blow as he muses that no matter what happens, the truly strong will always survive. In the post credit scene, Garou sees Watchdog Man, Saitama is in the bathroom, and a Dragon-level monster named Gouketsu is revealed to be the one who defeated Genos. Sweet Mask's concert is attacked by monsters, a group of monsters are attacking a hospital where Mumen Rider and Tanktop Master are at, a monster named Nyan looks for Puri-Puri Prisoner, but the prisoners reveal that Puri-Puri Prisoner escaped prison to fight against the monsters, and two monsters named Gyoro Gyoro and Orochi have captured Metal Knight.