Juu Juuzawa is a tough kid in a rough town. One day, he is approached by an odd girl by the name of Ame, who claims that she was connected to him in a past life and insists on serving as Juu's knight. His first reaction is to ignore her, distancing himself as quickly as possible. However, when a serial killer murders one of Juu's classmates and Ame seems to know something about the killings, he is forced into cooperating with her to get to the bottom of the mystery. Can this enigmatic stranger really be trusted?