Nenta, the older brother, lives an almost reclusive life, yet shares a strange relationship with his younger sister, Nenne. Though Nenne knows their bond is wrong, she can't bring herself to let go of Nenta's gentle presence. While they've stopped full intercourse, they continue engaging in oral sex. One day, Kameda, Nenta's longtime friend, pays a visit. Intrigued by Nenne's big tits, he begins blackmailing her, threatening to expose her relationship with Nenta, and starts manipulating her into submission. As a result, their twisted relationship grows even more complicated.