Recently noticing her weight gain, Rinka began stretching to combat her lack of exercise. However, finding it difficult to do alone, she asked her son Naoki for help. But Naoki, in the throes of puberty, found his eyes drawn to Rinka's taut breasts and voluptuous big ass, gradually perceiving her not just as his mother, but as something more. Sensing his gaze, Rinka felt something deep within her begin to stir.