This is already the sixth chapter. You should start from the first one.
I still don't understand why the MC doesn't admit that he was absolute ass at drumming and that's why he got kicked. What did he wanted the other band mates to do? They can't stop an album production to have the guy take drumming classes or some shit.
He admitted it immediately, that he's not good enough. He knows it. He doesn't suck, he's just not that good, with little further potential. The thing with the band, he did spend a decade to create and develop the band with the other members, but it was suddenly taken all away from him. You'd need to have the emotional capacity of a fish not to be pissed off and depressed after that.
What would you have him do? Not play drums at all in his second life? He might not be the most talented, but he did enjoy it and wants to keep doing it, despite knowing his limits. Furthermore, he wants to change Shigure's future as well. She'll be dead in 10 years otherwise.