Saitama is a hero who only became a hero for fun. After three years of “special” training, though, he’s become so strong that he’s practically invincible. In fact, he’s too strong—even his mightiest opponents are taken out with a single punch, and it turns out that being devastatingly powerful is actually kind of a bore. With his passion for being a hero lost along with his hair, yet still faced with new enemies every day, how much longer can he keep it going? Stream One-Punch Man free in HD on Gemflix — no signup, no account. 2015 · 3 seasons · Animation, Comedy, Action & Adventure, Sci-Fi & Fantasy. One-Punch Man seasons: Season 1 (2015, 12 episodes), Season 2 (2019, 12 episodes), Season 3 (2025, 12 episodes).