Having apparently trained himself to superhuman condition, Saitama faces an existential crisis as he is now too powerful to gain any thrill from his heroic deeds.
He registered with the Hero Association as a C-Class and eventually made a big leap to become a B-Class Superhero and is tasked to defend Z-City against Mysterious Beings. Under the Hero Association, he is given the name Caped Baldy (ハゲマント, Hagemanto).
Sword of Kings Storyline
He is a secundary hero in Sword of Kings 3nd saga and 4nd saga. He is most powerful human hero alive on multi-universe and is one of the top 10 most powerful heroes on Alliance of Freedom. He is the one of the top 10 target of the entire Balam Alliance.