I need some sauce

The story starts from a beta doctor the uke in the story (broken one I think). Then he met this popular alpha guy a part of a band I think.. then the really first time they met something snap inside them and they do the *thing* after that the alpha promised this beta that he will take the responsibility.

Then fast-forward this beta doctor discovered that he undergoes to a genetic mutation and became a Omega

I forgot about its tittle so please can someone give me the sauce