Dayumi and Arisa are a couple who were studying together at Arisa's house. Arisa's mother Yurihana is kind and beautiful, wearing clothes that emphasize her large breasts, and even though they know she's just a friend's mom, Dayumi can't help but get aroused by her presence. While using the bathroom, Dayumi accidentally catches sight of Yurihana masturbating intensely, calling out his name while pleasuring herself like she was Arisa incarnate. As he watches her, he becomes increasingly turned on until he reaches climax without actually ejaculating. Feeling frustrated yet unable to think about anything else besides Yurihana, he returns to the room where they had been studying earlier.