Ever since Shinya witnessed his stepmother Sasa indulging in masturbation in the bathtub, he was no longer satisfied with just watching. "If you're feeling lonely and want a man, then I'll be the one... But even though we're step-daughters, we're still father and son..." Shinya could only feel anguished. Meanwhile, Sasa, never dreaming that her daughter was struggling with such a dilemma, asks him to help clean the bath. The bathroom he always peeked into. The body he longed for was right in front of him. Shinya couldn't control himself...