After the sudden death of the matriarch of the Nakata family, her son, Kyō, struggles to come to terms with her passing and drifts through life in despair. One day, his father announces his decision to start a new life with Mio, a new partner. Kyō demands that Mio submit to him if she wishes to become part of the family, forcefully taking her body against her will. Though she resists, Mio ultimately ends up receiving creampie after creampie. From that moment on, Kyō's behavior spirals out of control, while his father silently condones his actions from the shadows. Gradually, the two conspire together to dominate and train Mio in perverse acts—including titty fucks and relentless creampie sessions—turning her into their personal milf plaything. This twisted family's daily life plunges deeper and deeper into an endless darkness with no escape in sight.