Narumi accidentally witnesses her son masturbating. She can't stop thinking about her grown-up son's hard cock, so she starts masturbating in her bedroom. Her son feels something's off when he hears some noises coming from his mother's bedroom and sneaks in. He also witnesses his mother masturbating. When her son says he can't take it anymore, her mother accepts, saying "Just once." But her son isn't satisfied with just one time, and begs for anal sex, saying "This is a good place, isn't it?"