Nao, a married woman who has been married to her husband for several years. - Her coldness increased compared to when she was married, and she felt lonely at her distance from her husband, who kept away from her. - Nao plans dinner on her husbands birthday in an attempt to restore her relationship with her husband. - Nao wants to celebrate the day with her beautiful appearance. By chance, Nao decides to see the leaflet of her swimming class in her eyes. - Nao is gradually fascinated by her kindness, which is different from her instructor, Arikis husband, in her swimming class. - And she never knew that a swimming class for her husband would upset the couple ...