Little Sister Netori My Heart And Body Belongs Here

This is a popular variant. The sister’s boyfriend cheated on her . She is heartbroken. You swoop in as the "consolation prize." You heal her wounds, but in doing so, you rewire her brain. She no longer wants a normal boyfriend; she wants the obsessive love only you provide. "He broke my heart, Onii-chan. But my body? I only want you to have it."