After three years of rigorous training, the ordinary Saitama has acquired immense strength, enabling him to defeat anyone and anything with a single punch. He chooses to apply this new ability for good by becoming a hero. However, he soon grows bored of effortlessly vanquishing monsters and seeks an opponent who can challenge him, hoping to reignite the thrill of heroism. Witnessing Saitama's extraordinary power, Genos, a cyborg, resolves to become his apprentice. During this period, Saitama recognizes that he lacks the recognition he feels he deserves and remains unknown to the public because he is not affiliated with the Hero Association. Aiming to improve his standing, Saitama agrees to let Genos register him, on the condition that he accepts Genos as a pupil. Together, the pair begin their ascent toward becoming true heroes, hoping to encounter formidable foes and gain respect along the way.