The story revolves around Saitama, a bald superhero who, at the age of 22, trained so diligently that he lost all his hair. However, he now has the ability to defeat any enemy with just one punch. Saitama is incredibly strong and easily wins all his battles. It is precisely because of this circumstance that he becomes bored. The main character resides in the abandoned district of Z City, which has been deserted by its residents due to the frequent appearance of hostile monsters.