Aoi, a married woman who has been married to her husband for three years. She felt lonely with her husband's demeanor, which was far from her initial kindness. When she goes shopping for her dinner with her worries, she happens to meet her classmate Hosoda from her school days. There, she learns that Hosoda works at a swimming class, and Aoi decides to attend her swimming class when she is invited to come and see her. After that, Aoi begins to be attracted to Hosoda's kindness, which encourages her husband's troubles every time she goes to her swimming class. And on the day her dissatisfaction with her husband explodes, Aoi crosses the line with Hosoda...
