Currently you are able to watch "One-Punch Man" streaming on Netflix, Hulu, Netflix basic with Ads or buy it as download on Apple TV, Amazon Video, Vudu, Microsoft Store, Google Play Movies.
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?