Kitaoka Karin plays a younger sister who has been targeted for many years by her perversely obsessed stepbrother. Her nipples have been relentlessly monitored since she was a child, and they have become so sensitive that she can reach orgasm with just a touch of her brother's fingertips. In a closed room, away from her family's eyes, she arches her body as her nipples are stimulated, leaving her with no way to escape, and she screams voicelessly as she repeatedly reaches orgasm. Her abnormal sensitivity is born from her forbidden obsession, and her immature vagina trembles in desire for her brother's cock. This is a story of family incest filled with a sense of immorality.