Tatsuya is desperate to have sex with his girlfriend, but due to the circumstances of being at her home, he has no choice but to restrain himself, leaving him restless. One day, while heading to the toilet, he passes through the living room and accidentally catches his girlfriend's mother, Kumi, masturbating in the kitchen. Even more shockingly, Kumi is calling out Tatsuya's name as she pleasures herself. Shortly afterward, when he walks through the living room again, he encounters Kumi relaxing in nothing but a bath towel. During their conversation, the towel slips off her body, exposing her naked skin, and Tatsuya can no longer hold back, lunging at her uncontrollably. At first, Kumi resists, but when Tatsuya points out that he saw her masturbating while calling his name, her resistance quickly crumbles.