Single mother Keiko finds her door unlocked when arriving home early from work. Puzzled, she quietly walks in and witnesses her daughter Mayu fooling around with another girl. Embarrassed by what she's seen, Keiko pretends not to notice and acts normally around them.

Mayu later introduces the girl as her classmate and girlfriend Saori. Keiko has no objections to their homosexual relationship and even allows Saori to stay the night, despite knowing the young couple may continue their sensual acts. However, as Mayu drifts off to sleep, Keiko gets an unexpected visit from her daughter's girlfriend while bathing…