The wife of an obstetrician, Ryouko, and the wife of an internist, Nanako, are both unsatisfied with their marriages and decide to swap husbands. Each comes up with an excuse to visit the other's husband for a medical examination. Nanako pretends to need a pregnancy test and lies on the examination table, where her brother-in-law manually inspects her genitals, giving her a quiet, secret pleasure. Meanwhile, Ryouko becomes aroused during her examination by her brother-in-law and begins craving new excitement. Later, when the two wives return for another visit, they pass by the brothers chatting in the office after closing. Holding onto their secret, the two women's choices to change their marital relationships spark a new development.