Miki has been married to her childhood friend Hiro for 10 years, but recently Hiro has become cold towards her and has been going out drinking every day. Her sexual relations with her husband are becoming less and less frequent, and she feels increasingly lonely. The only thing that supports her Kokoro is her stepfather, Tohru, who lives next door. Tohru was her homeroom teacher in her school days and was always kind to her, and her old feelings for him are revived. Before she knew it, Miki had been subtly seducing Tohru, so she made up her mind and headed to her stepfather's bedroom...