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. Though he’s now so strong he can defeat any opponent with a single punch, lately he feels as if, in exchange for overwhelming power, he’s lost something even more important.

A monster is moving toward City Z, one that has been created by the mysterious organization known as The House of Evolution. Genos, a young cyborg, attempts to stop it, but gets in over his head before Saitama happens along.

Saitama and Genos glean information about The House of Evolution and its founder Dr. Genus, a scientist with dangerous ideas on artificial human evolution. Meanwhile, Dr. Genus 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, led by an enormous man known as Hammerhead. Calling for the redistribution of wealth, the group targets the fat-cat Zeniru, who in turn dispatches his bodyguard to defeat them. Unfortunately, Saitama is on the same errand.

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, but first he must pass the Hero Association tests and become a full-fledged member.

It’s been five days since Saitama became a professional hero and he has yet to do anything heroic. When Genos informs him that C-class heroes who don’t fight bad guys are dropped from the hero registry after a week of inaction, Saitama heads out on patrol, yet can’t 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. When all their efforts prove in vain, Genos decides it’s up to him to protect the home of his master and stop the meteor, no matter what the cost.

A pack of monsters calling themselves the “Clan of the Seafolk” arrive on the shores of City J intent on invading the land. When the hero sent to fight them is defeated easily by the Deep Sea King himself, Saitama and Genos head for the city to help.

As the battle with the Deep Sea King reaches its climax, more heroes fall to the aquatic despot’s brutal attacks. Which of them has what it takes to be a true hero?

A story about Saitama from when he still had hair and his only costume was a track suit. Several shops in Saitama’s neighbourhood have gone out of business and the owner of the last one left needs his help.

Saitama tags along to an emergency meeting of Class S heroes and discovers that a seer has foretold a serious danger threatening the Earth. Though the crisis could occur anytime in the next six months, the heroes are surprised to hear the roar of explosions that very hour!

As a colossal spaceship floats in the skies above City A, a member of its monstrous crew battles on the ground against a group of S Class heroes. Despite their powers, they can’t seem to finish it off. Meanwhile, Saitama has boarded the enemy ship on his own.

The inconceivably powerful Lord Boros has traveled untold distances in search of someone who can cure his boredom: Saitama! With the fate of humanity in the balance, will the two champions at last find in each other the worthy opponent they’ve been searching for?

A story set sometime between Mosquito Girl’s defeat and Genos showing up to Saitama’s apartment. Genos wants to learn the secret to Saitama’s power and decides to follow him and to observe everything he does. At the same time, Saitama is convinced that someone is stalking him.

Jenosu it accidentally trapped in Don Pacino a little bit caught in the Mafia of conflict. Jenosu that are in a hurry the shopping asked the bargain in Saitama’s to explain to Don Pacino, but…

Sonic strive to strict training muffled to the mountain, but had spent the days of troubled with nightmares to be a nasty blow to the groin from Saitama who suffered a defeat. Man of Matagi had seen such a situation. He is also “formidable enemy” in defeated in the past of the owner…

After the events of episode 7, Bang begins to spy on Saitama and Genos to gauge their abilities. Hopeful that his Water Stream Rock Smashing Fist martial arts is stronger, and that proving so will coerce Saitama and Genos to study under him, Bang invites Saitama and Genos to his dojo under the pretense of giving them free meat.

During a coincidental train ride, Genos and Fubuki are put to the test when an anti-Hero Association group plants a bomb on the train.

Child Emperor investigates the murder of Zombieman. When Saitama is put under suspicion, Genos promises that he will vouch for Saitama even if he’s the culprit.

One Punch Man 2nd Season’s commemorative recap special.

Saitama meets a group of villains in a public restroom who mistake him for their ally, they introduce themselves to Saitama, but when he reveals he’s a hero, attempt to defeat him.

Atomic Samurai and Bang go out fishing to a lake.

As Genos and Saitama watch TV, Saitama accidentally knocks Genos out trying to reach his potato chips and Genos wakes up with memory loss.

Saitama brings Genos to a tournament for the fighting video game “Wild Animals” due to the grand prize being five million yen. Several locations all over the country are being used as venues, and the battles take place online.

One stormy night, a monster emerges from a junkyard and begins making its way towards Smelly Lid Prison. Noticing its approach, Puri-Puri Prisoner breaks out of his cell and quickly defeats the monster. However, he damages the prison’s electricity in the process, allowing a handful of inmates to escape.

Child Emperor, Zombieman, Superalloy Darkshine, and Metal Bat are dispatched to a forlorn, snowy mountain to hunt down a monster.