The seemingly unimpressive Saitama has a rather unique hobby: being a hero. In order to pursue his childhood dream, Saitama relentlessly trained for three years, losing all of his hair in the process. Now, Saitama is so powerful, he can defeat any enemy with just one punch. However, having no one capable of matching his strength has led Saitama to an unexpected problem—he is no longer able to enjoy the thrill of battling and has become quite bored. One day, Saitama catches the attention of 19-year-old cyborg Genos, who witnesses his power and wishes to become Saitama's disciple. Genos proposes that the two join the Hero Association in order to become certified heroes that will be recognized for their positive contributions to society. Saitama, who is shocked that no one knows who he is, quickly agrees. Meeting new allies and taking on new foes, Saitama embarks on a new journey as a member of the Hero Association to experience the excitement of battle he once felt.

Eighth-grader Shigeo Mob Kageyama has tapped into his inner wellspring of psychic prowess at a young age. But the power quickly proves to be a liability when he realizes the potential danger in his skills. Choosing to suppress his power, Mob's only present use for his ability is to impress his longtime crush, Tsubomi, who soon grows bored of the same tricks. In order to effectuate control on his skills, Mob enlists himself under the wing of Arataka Reigen, a con artist claiming to be a psychic, who exploits Mob's powers for pocket change. Now, exorcising evil spirits on command has become a part of Mob's daily, monotonous life. However, the psychic energy he exerts is barely the tip of the iceberg; if his vast potential and unrestrained emotions run berserk, a cataclysmic event that would render him completely unrecognizable will be triggered. The progression toward Mob's explosion is rising and attempting to stop it is futile.

After dying a laughable and pathetic death on his way back from buying a game, high school student and recluse Kazuma Satou finds himself sitting before a beautiful but obnoxious goddess named Aqua. She provides the NEET with two options: continue on to heaven or reincarnate in every gamer's dream—a real fantasy world! Choosing to start a new life, Kazuma is quickly tasked with defeating a Demon King who is terrorizing villages. But before he goes, he can choose one item of any kind to aid him in his quest, and the future hero selects Aqua. But Kazuma has made a grave mistake—Aqua is completely useless! Unfortunately, their troubles don't end here; it turns out that living in such a world is far different from how it plays out in a game. Instead of going on a thrilling adventure, the duo must first work to pay for their living expenses. Indeed, their misfortunes have only just begun!

In the wake of defeating Boros and his mighty army, Saitama has returned to his unremarkable everyday life in Z-City. However, unbeknownst to him, the number of monsters appearing is still continuously on the rise, putting a strain on the Hero Association's resources. Their top executives decide on the bold move of recruiting hoodlums in order to help in their battle. But during the first meeting with these potential newcomers, a mysterious man calling himself Garou makes his appearance. Claiming to be a monster, he starts mercilessly attacking the crowd. The mysterious Garou continues his rampage against the Hero Association, crushing every hero he encounters. He turns out to be the legendary martial artist Silverfang's best former disciple and seems driven by unknown motives. Regardless, this beast of a man seems unstoppable. Intrigued by this puzzling new foe and with an insatiable thirst for money, Saitama decides to seize the opportunity and joins the interesting martial arts competition. As the tournament commences and Garou continues his rampage, a new great menace reveals itself, threatening the entire human world. Could this finally be the earth-shattering catastrophe predicted by the great seer Madame Shibabawa?