Hi,friends, have you read Boku wa Imouto ni Koiwosuru yet? This manga is really amazing, I never thought I would like this.

Yori's attitude has changed. He and his twin sister, Iku, used to be inseparable as children, but lately Yori's been different -- eager to be apart from Iku. Iku worries that he hates her, but the truth is far more scandalous. Now, Yori would risk losing everything to have his little sister. Iku loves her big brother enough that she would never risk losing him, and so she'll do what it takes to keep them together... but Yori doesn't want to have her that way -- as a sister dedicated to her twin. Can Iku ever love Yori not as a brother but as a man?

I personally like mangas that have themes of "incest" but I don't really approve of it in real life but it doesn't concern me just as long other ppl don't know if they're related and not show too much public affection. And there is a movie real life based off of this manga with Jun Matsumoto and another actress.
Address:
http://emanga1.isoshu.com/bookinfo/27045/?recommid=2006