Episode 21

"The Strongest Troubles" is the twenty first episode of the One-Punch Man anime series and ninth episode of season two.

Summary
Bakuzan recognizes Saitama as the one who defeated him, but Saitama kills Bakuzan in one punch. Saitama formally introduces himself to Suiryu as a hero and explains that he joined the martial arts tournament to find the hero hunter as well as experience martial arts. Saitama plans to leave but Suiryu begs Saitama not to because Gouketsu is out there. Saitama ignores him nonetheless. Suiryu hears multiple shock waves, and believes Saitama is killed until Gouketsu's decapitated head lands in front of him. Saitama returns and asks Suiryu to not tell anyone what happened, and Suiryu asks if he could become a hero. Saitama agrees, since a nobody like himself can become a hero. Suriyu also asks to be Saitama's disciple, to which Saitama declines. Puri-Puri Prisoner manages to defeat a demon-level monster called Free Hugger by hugging it so tightly that it dies. Puri-Puri Prisoner receives a call that his cell mates were captured by monsters. After talking to C Class Water Gun, Saitama has an existential crisis by reflecting that his experience with martial arts and the Hero Association still left him bored. King meets up with Saitama and tries to explain that Saitama was so focused on being the strongest hero, he lost track of himself and should aim to be the best hero. Saitama declines, saying that it sounds boring but just when he gives up hope King offers to play against Saitama using only two fingers, rekindling Saitama's drive. Garou is defeated by Watchdog Man due to the unpredictable fighting style of Watchdog Man, but is filled with adrenaline on what he can learn. Garou sees King, and is about to hit him when Saitama kicks Garou into a concrete wall. Saitama mentions that there are news of a hero hunter, and can't wait to meet him. Genos is taken in for repairs to Dr. Kuseno. Meanwhile, Speed-o'-Sound Sonic is training when he is attacked by two very powerful ninja warriors named Gale Wind and Hellfire Flame, who offer Sonic monster cells to become stronger. Sonic plans to eat the monster cells, but due to him cooking the monster cells he doesn't undergo transformation and has diarrhea instead. S Class Hero Rank 8 Zombieman sees Martial Gorilla, and is about to follow him when Armored Gorilla encounters Martial Gorilla. Armored Gorilla knocks out Martial Gorilla, so Zombieman decides to follow Armored Gorilla instead. Bang and Bomb talk about Garou, and a monster infiltrates a member of the Hero Association to give them a message.

Trivia

 * This episode should have aired on June 4th, 2019 but was delayed by one week due to the French Open 2019, a tennis competition, being scheduled at the same time.