Kagami lost her parents and has been surviving alongside her brother, Yuuki. To deepen her brother's affection, she developed an interest in anal. Their relationship was bound by a twisted connection where love and obsession intertwined. One day, Yuuki's engagement was suddenly arranged. Upon learning this, Kagami spitefully became engaged to another man. However, she could no longer be satisfied with just her brother. When Kagami decided she no longer wished to marry and requested to end the engagement, her fiancé, Ieoi, presented a shocking condition as compensation...