the manga is about a guy living alone, and his younger sister, who is a lesbian, moved in with him.
his sister transfered to a school near his house, and fell in love with her teacher (female).
in the manga, he got a girlfriend who sings for a rock band. i think they met in a group date, and started to go out. the girl loves him a lot and knows that he once had sex with his younger sister's ex- girlfriend. but she pretends she didn't know because she was afraid of him leaving her.
the manga contain mature content (sexual intercourse and lesbian stuff).
the story mainly revolve around the guy, his girlfriend (the singer), and his sister's ex-girlfriend.
i think that a few years back, it is rumored that the mangaka has stoped the manga.
hope the information i provided helps.
thanks in advance. =D
please pardon my bad english.