Ani ga Imouto de Imouto ga Ani de.

Taiyô is 16 years old and he loves talking. then his sister, Hikari is also 16 years old but she's a bit dark. they didn't know that their secret will be expose but it will explode their fraternity. But then his sister decides to attack him.but she has no one to tell...no, there's no one who can really believe it, right?