Her son's husband worked as a taxi driver, and due to his irregular schedule, their marital relationship had completely broken down after the birth of their child. Ryoko began to feel lonely. One night, she accidentally discovered her son masturbating. At that moment, strong maternal feelings welled up inside her—but alongside them, an uncontrollable desire began to stir. She ended up assisting her son's masturbation, though it wasn't out of mere affection, but rather to satisfy her own craving. That night, she stuffed his cock into her mouth, seeking her own pleasure. This impulse, born at the intersection of motherhood and sexual desire, guided her and became the starting point of a new relationship.