The Strongest Man
Saitama is a guy who's a hero for fun. After saving a child from certain death, he decided to become a hero and trained hard for three years.
The Terrifying City
When Saitama learns that C-class heroes who don't fight bad guys are dropped from the hero registry after a week of inaction, he heads out to find any criminals or monsters to stop.
The Ultimate Disciple
An enormous meteor hurtles toward City Z, forcing the Hero Association to ask its S Class heroes to respond.
Saitama tags along to an emergency meeting of Class S heroes and discovers that a seer has foretold a serious danger threatening the Earth.
The Dominator of the Universe
As a colossal spaceship floats in the skies above City A, a member of its monstrous crew battles on the ground against a group of S Class heroes.