The seemingly unimpressive Saitama has a rather unique hobby: being a hero. In order to pursue his childhood dream, Saitama relentlessly trained for three years, losing all of his hair in the process. Now, Saitama is so powerful, he can defeat any enemy with just one punch. However, having no one capable of matching his strength has led Saitama to an unexpected problem—he is no longer able to enjoy the thrill of battling and has become quite bored.

One Punch Man

It is August 12th. After the remote control to his boarding house's only air conditioning unit is inadvertently destroyed by spilled cola, "I" devises a plan to return to yesterday in a time machine to recover the remote before it breaks. However, his prankster friend Ozu cannot resist playing with past events, even if it means bringing the universe to the brink of destruction. Now "I" finds himself racing through time to avoid disaster.