Shiho gave birth to her son, Yuki, when she was 20 years old. As Yuki grew older, the couple's sex life became less and less fun, but Shiho's libido increased. However, one day she discovered that her husband was cheating on her, and their relationship quickly became strained. After Yuki entered university, they began discussing divorce, and all that remained was to file the papers. When Yuki returned home for summer vacation, Shiho waited for her son at the station to tell him the news before filing the papers.