A Thing Hiding in a Erotic Cult

Tooru and his sister Yume end up in the hospital after a traffic accident, leaving their father brain dead. Suddenly, Itou Yuuzen appears out of nowhere and takes them under his "religious cult's" protection. Is this the beginning of a new life for the brother and sister, or is something hiding behind the facade of this religious cult? Note: Includes 9 extra chapters.