Miki Uesugi is a young married woman who graduated from a physical education university and once won first place in her prefecture's swimming competition during her school days. Currently, she works alongside her husband and teaches at a nearby swimming school. On weekends, she enjoys surfing and has a very relaxed personality. Although she gets along well with her partner, their relationship has gradually become sexless over time. They agreed to use condoms during sex, but ultimately end up breaking that promise. Working at the swim school keeps her body toned and exuding youthful charm. A new relationship begins—impregnating her with seed.