One day, when Reiko gets out of the bath, she finds her daughter's boyfriend standing in the dressing room, holding her underwear. Though both are surprised by this sudden event, they manage to keep things together and act as if nothing happened. However, Reiko is unaware that her boyfriend is thinking naughty things with her underwear. To her boyfriend, Reiko's naked body is more beautiful than his daughter's, and this ignites the flames of lust in both of them. Unable to contain herself, he makes a advance on her, and although she feels bad, she is driven by the throbbing in her body that won't subside...