Episode 17

"The Martial Arts Tournament" is the seventeenth episode of the One-Punch Man anime series and fifth episode of season two.

Summary
Metal Knight attempts to battle Elder Centipede by firing missiles, but fails to make even a scratch. After a lengthy battle Garou seemingly beats Metal Bat, but grudgingly admits that Metal Bat would have won if he hit him once. To Garou's surprise, Metal Bat gets up and nearly kills Garou when Garou's back was turned, but stops when his younger sister, Zenko, finds him. Garou counter attacks, and is about to hit Metal Bat when Zenko gets between them and orders them to stop fighting due to a promise of Metal Bat never showing violence to Zenko. Garou relents (having a soft spot for kids) and walks away to find Watchdog Man. Metal Bat attempts to confront Elder Centipede but collapses due to too much damage from his battles with Elder Centipede and Garou. The two C Class heroes (Pineapple and Mohican), who have the unconscious Narinki and Waganma, are confronted by Rhino Wrestler and are both swiftly defeated, which causes the monsters to capture Waganma.

Sludge Jellyfish oozes his way towards Zenko to use as a hostage but is blasted apart by Garou. Garou prepares to fight but Phoenix Man calls for a ceasefire. The two monsters try to persuade Garou to join the Monster Association, but Garou refuses. Phoenix Man promises Garou that they will meet again if Garou continues to hunt for heroes, and tells Elder Centipede and the rest of the monsters to retreat, with Metal Knight attaching itself to Elder Centipede and following them. Bang and Bomb are trying to find Garou, and Bang lets out his frustration on a monster named Fist Fight Djinn, killing him violently. Many monsters of different disaster levels (Marshall Gorilla, Do-S, Hundred-Eyes Octopus, Pureblood, Maiko Plasma and more) simultaneously attack heroes, stretching the heroes force thing which alarms the Hero Association. Before Do-S could kill Dynamite Man (her power being that if she whips someone, they will be under her control) with her mind controlled heroes, Fubuki stops her attack. Meanwhile in the Super Fight Tournament where Saitama is introduced to Bakuzan, Suiryu, Lightning Max, Lin Lin, Hamukichi, Choze, Zakos and Sneck with Genos in the crowd. Suiryu notices Bakuzan's bloodlust towards him, and is only after the prize money, although Suiryu wished he could have fought against WolfMan (Garou at the time). After Lightning Max defeats Lin Lin, Zakos reveals that the fighters are often paired up based on their apparent strength. Saitama deduces that Zakos is weak since he's paired up with Saitama (Saitama being sorted due to him appearing "weak.") which angers Zakos. In the post credits, Saitama slaps Zakos in one hit, winning the battle much to Saitama's annoyance. Suiryu notices Saitama's strength and is excited that he will face Saitama in the finals.