Having a slutty sister-in-law like Yui Hatano is the dream of most men, but for her brother-in-law, it is the opposite. He just hopes that she will behave properly with her role in the family. But life is not like a dream. The more gentle and decent he acts, the more she takes advantage of him and continuously seduces him with her plump body and seductive pajamas. Many times, she even dared to rape him to the point that sex is like her daily meals. Gradually, it also becomes a habit, an unbreakable habit, it makes him deeply absorbed into the dark path of incestuous affairs between the two.