Miwako, a married woman living in an apartment complex, somehow gets along well with Kasumi, who lives next door. Kasumi is shocked when she sees her stepmother Yasuyo engaging in lewd acts with her father, and confesses that she left home to go to a female friend's house. Then Kasumi is kidnapped, and the kidnapper designates Miwako as the person to negotiate a deal with. Yasuyo and her husband gather in Miwako and her husband's room, who are not aware of the incident, and they spend an uneasy night together. This strange incident brings about complex changes between the two couples...