Aoi, a woman who has been married to her husband for three years. Away from the original kindness, she felt lonely at her husband's attitude. When she went shopping for dinner with her worries, she happened to meet Hosoda, her classmate when she was a student. There, she knew that Hosoda was working in a swimming class, and Aoi was invited to visit her and decided to go to her swimming class. After that, every time he went to the swimming class, Aoi began to be attracted to Hosoda's kindness, which encouraged her husband's worries. And on the day when her dissatisfaction with her husband exploded, Aoi passed the boundary with Hosoda.