Futaba-san Chi no Kyoudai

Neiko Futaba is the school idol, but little does everyone at school what's she's really like. Only her beloved younger twin brother Otohiro knows her overly clingy persona, much to his dismay. On top of that, it seems Neiko seems to be rather determined to seduce her brother in every way possible. Unfortunately (or fortunately) for Otohiro, it is...