[Screenshot]
[Storyline]
Dopo tre anni di allenamento, un ragazzo venticinquenne di nome Saitama ha raggiunto il suo obiettivo: essere un eroe talmente forte da poter sconfiggere chiunque con un solo colpo. Tuttavia, essere diventato così potente ha reso talmente facile il ruolo di eroe a Saitama da renderlo perennemente annoiato e portarlo alla depressione. In seguito, con la conoscenza del cyborg Genos (che diventerà suo allievo), entrerà a far parte dell'Associazione Eroi, un'organizzazione che riunisce gli eroi della Terra con lo scopo di combattere criminali, mostri e disastri vari. Il nuovo obiettivo di Saitama diventa quello di scalare le classifiche dell'associazione e diventare uno degli eroi più popolari.
[Storyline]
On a supercontinent Earth, powerful monsters and villains wreak havoc in the cities. In response, the millionaire Agoni creates the Hero Association, which employs superheroes to fight evil. Saitama, an unassociated hero, hails from City Z and performs heroic deeds as a hobby. He has trained himself to the point of being able to defeat any enemy with a single punch, but his unmatched strength has left him with an overwhelming sense of boredom. He becomes a reluctant mentor to Genos, a cyborg seeking revenge against another cyborg who killed his family and destroyed his hometown, after saving him from a monster. Saitama and Genos join the Hero Association in hopes of attaining notability, but due to scoring low on the written entry exam, Saitama is placed at a low-entry rank, and his feats remain unnoticed by the public even when he saves people from two colossal disasters.
Shortly before his death, the seer Shibabawa predicts that the world is in great danger. The Hero Association alerts its top heroes just as the alien Boros invades the planet. The heroes kill the alien forces and destroy Boros's ship. Saitama then slays Boros in single combat, although he notoriously takes multiple punches to kill. In the aftermath, Saitama meets heroes like the martial artist Bang and esper Blizzard.
Monsters begin appearing at a growing rate while the rogue martial artist Garo, Bang's former apprentice and self-dubbed "Hero Hunter," begins terrorizing heroes due to holding a grudge against everything "heroic" from childhood bullying.
The monster influx is revealed to be the doing of the Monster Association, an organization of monsters under City Z that is intent on destroying the Hero Association. They attack various cities, kidnap a Hero Association executive's child, and recruit fighters by offering them "monster cells" that, when eaten, cause them to mutate into monsters with extraordinary abilities. Garo bonds with a child who idolizes heroes as he hunts down more and more heroes, his combat prowess slowly rising. The Monster Association attempts to recruit him and kidnaps the child when Garo refuses, leading him to storm the Monster Association headquarters trying to rescue the child, where he is ultimately captured. The Hero Association assaults the headquarters to rescue the captive children and a chaotic battle ensues, destroying City Z. Almost every monster is slain in battle, with Blizzard capturing Psykos, her childhood friend and the mastermind of the organization. Saitama meets the extremely powerful hero Blast during the raid when he arrives to collect artifacts, who warns him of a threat only known as "God." Many of the heroes are heavily injured when Garo emerges, having mutated into an immensely powerful monster. He effortlessly defeats the remaining heroes when Saitama arrives and confronts him, managing to destroy his monster mutation and revert him to a human after a brutal battle. Despite the objections of the other heroes, Saitama spares Garo and lets him flee after his befriended child stops them.
In the aftermath of the battle, the Hero Association's poor performance causes public opinion of them to plummet. Several heroes and officials decide to retire or defect to the Neo Heroes, a burgeoning rival group that appears more effective in handling the growing monster threats with its larger membership and the leadership of the hero Blue, who claims to be the son of the Blast.
