One Punch Man, Vol. 3

One. One Punch Man, Vol. 3. 2015. 210p. ISBN 9781421564616. 

Saitama is the strongest man alive, and he has defeated all monsters who have attacked him with one punch. But no one knows who he is, and as a result he lives in a run-down section of town and must shop for bargains. Now that Genos is in his life as his apprentice following One Punch Man, Vol. 2, Saitama learns of the Hero Association, the group that most heroes have joined. Heroes are ranked on their prowess, abilities, and results, and are compensated and celebrated based on that rank. Genos successfully convinces Saitama to take the placement test. While Genos scores a perfect 100% and is immediately ranked S-class, Saitama barely passes with a 71%, and is ranked C-class. His strength, however, is unparalleled. 

With their Hero Association card in their pockets, Saitama begins Genos' training in earnest, but through it all he thinks he's a fraud, for he has really nothing to teach Genos aside from the fact that hard training is what made him powerful. Genos, however, refuses to accept this truth, and continues to search for Saitama's secret. He even moves in with Saitama, hoping to learn more from him. To keep his rank, Saitama wanders the city, looking for opportunities to be a hero ...

The story continues in One Punch Man, Vol. 4.