Episode 21

Bakuzan recognizes Saitama as the fighter who beat him, and Saitama ends him with a single punch. He then introduces himself to Suiryu as a hero, explaining that he entered the tournament to track the hero hunter and sample martial arts. As he moves to leave, Suiryu begs him to stay because Gouketsu is still loose, but Saitama walks off anyway. A series of shock waves makes Suiryu fear the worst until Gouketsu's severed head lands in front of him. Saitama returns, asks him to keep the matter quiet, and, when Suiryu wonders whether he could become a hero too, encourages him that even a nobody can, though he turns down the request to take him on as a student.

Puri-Puri Prisoner smothers the demon-level Free Hugger to death in a crushing embrace, then learns his cellmates have been seized by monsters. After a chat with the C-Class hero Water Gun, Saitama sinks into an existential slump, still bored despite everything. King finds him and argues that his fixation on being the strongest has cost him himself, urging him to aim at being the best hero instead. Saitama shrugs it off until King offers to play him using only two fingers, which instantly relights his competitive fire. Garou, beaten by Watchdog Man's erratic style, comes away energized by how much he could learn, and when he spots King and moves to strike, Saitama kicks him through a concrete wall before noting he cannot wait to meet the hero hunter. Genos is delivered to Dr. Kuseno for repairs. Meanwhile the ninjas Gale Wind and Hellfire Flame ambush a training Speed-o'-Sound Sonic and offer him monster cells, but Sonic cooks them first, avoids transforming, and merely gets a stomachache. Zombieman shifts his surveillance from Marshall Gorilla to Armored Gorilla after the latter knocks Marshall Gorilla out, while Bang and Bomb discuss Garou and a disguised monster infiltrates a Hero Association member to pass along a message.

Saitama kills Bakuzan and then Gouketsu, quietly ending the tournament threat, and inspires Suiryu toward heroism. King's two-finger handicap snaps Saitama out of his boredom. Garou is defeated by Watchdog Man but treats the loss as growth. Gale Wind and Hellfire Flame recruit toward Speed-o'-Sound Sonic with monster cells, and the Monster Association plants a message inside the Hero Association.

Bearing the title The Troubles of the Strongest, this episode spans the tail of the Super Fight Arc into the Monster Association Arc, adapting chapters 75 through 79. It aired in Japan on June 11, 2019, and in English on December 7, 2019, retaining Seijaku no Apostle and Chizu ga Nakute mo Modoru Kara. It had been slated for June 4 but was pushed back a week to avoid a scheduling clash with the 2019 French Open. The adaptation trims the S-Class heroes Genos imagines from eight down to four.