Although they are not related by blood, Yui's stepbrother has always been kind and caring towards her younger Yui. One day, her father goes on a company trip. As soon as they are alone after seeing her father off, her stepbrother changes completely. His twisted love is now directed towards Yui. Yui is confined in a room and toyed with. At first, Yui resists, but she is raped and brainwashed by her devilish brother, and falls into a twisted love...