Satsuriku No Tenshi

Storyline

13-year old Rachel awakens to find herself trapped in the basement of an unfamiliar building. Upon meeting a serial killer wrapped in bandages, she begs him to kill her. As his only wish is to leave the building alive, he agrees to do so if she would help him escape. A strange bond is struck between them, held by a bizarre promise. These two, trapped in this building, don't know why fate has placed them there. But they will work together desperately to find a way out.