One-Punch Man: The Hero That Doesn't Want Fame.
(WARNING: This fanfic is very old, and it's abandoned for a reason)
After Vaccine Man was defeated by Saitama, two heroes witnessed him killed Vaccine Man. The two random heroes reported this to the Hero Association. They decided to sent a S-Class hero to recruit Saitama to join the S-Class hero, but he refuses because he wasn't interested or not ready for recognition or fame, so they tried to beg him to be in S-Class but he still refuses, so they decided to put Saitama in C-Class hero, but in reality, he was actually an S-Class hero.
This is also a fic where Saitama uses multiple Serious Series techniques, lol.
(I admit, I love Saitama's serious techniques, even though they sound ridiculous and funny, they still sound pretty badass.)
Disclaimer: One-Punch Man belongs to the Creator, ONE.
