Iori is a married woman who works as an instructor at a swimming school. Her relationship with her husband has cooled since they first got married, and swimming in the pool is the only way she can release stress. At that time, her husband brought home a junior colleague, Sugimura, who she recommends to join her husband's swimming lessons. Iori, who usually teaches children, is conscious of her husband's muscular junior colleague, Sugimura, as a man. The same goes for Sugimura, who sees Iori in a swimsuit as a woman and crosses the line, forgetting that she is a married woman.