So, I remember reading this manga at least 3-4 years ago, maybe more.
There was this guy who for some reason started working in a bar, possibly a hostess club, though I don't remember for sure.
He also starts falling in love with a girl who works there, who seems naive and innocent, but later he discovers she's just playing him along.
Also I think that he had a trauma from when he was younger, because the girl he liked hooked up with his brother, and he heard them going at it in the room next to his.
It'd be amazing if anyone could tell me what manga it was, thanks in advance.