Himori and Arisa are a newly dating couple, and are having a study session at Arisa's house. Arisa's mother, Yurika, is kind, beautiful, and wears clothes that accentuate her breasts, and Himori is excited even though he knows that she is his girlfriend's mother. On his way to the bathroom, Himori peeks at Yurika masturbating vigorously. Calling out his own name, he plays with his own pussy and masturbates as if he is Arisa. He strokes his own erect penis while watching her mother masturbate, but ends up unable to ejaculate. He returns to his room in a frustrated state, but Yurika is the only thing he can think about.