Saitama, a seemingly ordinary man with a unique passion for heroism, becomes immensely powerful after rigorous training that costs him his hair. Now capable of defeating any foe with a single punch, he finds himself bored with the lack of challenge in battles. However, his mundane routine takes a turn when Genos, a young cyborg, seeks to become his apprentice. Together, they venture into the Hero Association to gain recognition for their heroic deeds. Saitama, longing for formidable adversaries and recognition, embarks on a quest to reclaim the thrill of combat and possibly attain fame.