Saitama is out shopping with Genos in tow when the pair come across G4, a demonic robot on a mission to eliminate King. Elsewhere, Sitch attempts to recruit various villains and assassins of the underworld to help the Hero Association.
Garou issues a declaration of war on the Hero Association through terrifying means, Hellish Blizzard gives Saitama an ultimatum, and Genos decides to eliminate his master's stalker, Speed-o'-Sound Sonic.
Garou, out hunting heroes, can barely contain his excitement when he gets the chance to battle the S Class hero Tank-top Master. Meanwhile, Silverfang shutters his dojo to begin his own hunt of his former disciple.
Assigned to guard a VIP and his son, Metal Bat couldn't be less thrilled. But when the group is suddenly attacked all hell breaks loose. Meanwhile, Saitama wears a disguise in order to enter the "Super Fight" martial arts tournament.
Monsters from the Monster Association launch simultaneous attacks on all the human cities, attempting to overwhelm the forces of the Hero Association. Meanwhile, the "Super Fight" martial arts tournament kicks off.
The Super Fight tournament kicks off while Genos takes on multiple monsters who have appeared in City C. Elsewhere, countless monsters are wreaking havoc in multiple areas causing the Hero Association to be overwhelmed.
As the Super Fight tournament heads for its grand finale, the Class S heroes battle to hold back the tide of monster incursions. Meanwhile, Atomic Samurai is setting in motion a plan of his own.
Goketsu, the first Super Fight Tournament champion, arrives in the stadium. Having now become a monster, he's aiming to force the Super Fight competitors to turn into monsters themselves. When some do, Suiryu must take them on alone.
Saitama is a guy who's a hero for fun. After saving a child from certain death, he decided to become a hero and trained hard for three years.
A monster is moving toward City Z, one that has been created by the mysterious organization known as The House of Evolution.
Saitama and Genos glean information about The House of Evolution and its founder Dr. Genus, who learns of Saitama's amazing strength and has plans of his own for One-Punch Man.
A group of battlesuit-clad terrorists called "The Paradisers" appears in City F, and targets the fat-cat Zeniru, who in turn dispatches his bodyguard to defeat them.
Though he's been doing the hero gig for three years, Saitama realizes that the public knows nothing about him. Determined to get a little recognition, he decides to become a pro hero.
When Saitama learns that C-class heroes who don't fight bad guys are dropped from the hero registry after a week of inaction, he heads out to find any criminals or monsters to stop.
An enormous meteor hurtles toward City Z, forcing the Hero Association to ask its S Class heroes to respond.
Saitama and Genos head to the shores of City J to stop a pack of monsters calling themselves the "Clan of the Seafolk".
As the battle with the Deep Sea King reaches its climax, more heroes fall to the aquatic despot's brutal attacks.
Saitama tags along to an emergency meeting of Class S heroes and discovers that a seer has foretold a serious danger threatening the Earth.