Miki has been married to her childhood friend for ten years. Recently, Hiroshi often goes out drinking late and has become distant with her. Although Miki has chosen sexy outfits and wishes to have a child soon, her husband always finds excuses to refuse. As her feelings for her husband fade, the loneliness drives her to seek emotional support from her father-in-law, Toru, who lives next door. Her father-in-law was once Miki's homeroom teacher, who always treated her very well and helped lift her spirits during her toughest times. She spends more time with her father-in-law than with her husband, and her feelings for him grow stronger. Then one day, Miki takes the initiative to cross the line, doing something that leaves them unable to turn back...