Yumiko went on a hot spring trip for the first time in a long time during summer vacation with her son who came to Tokyo to attend university there. In fact, after her son came to Tokyo, Yumiko's husband was found to have been cheating and their relationship became cold. They are no longer a married couple and are on the verge of divorce, and this trip was to tell her son about it. In the middle of the trip, Yumiko tells him about the divorce. When her son finds out that his mother no longer belongs to anyone, he begins to seek his mother as a member of the opposite sex...