The story takes place in the city of Tokui, which has a legend of two monsters. Yūko Tengai transfers to the town's high school out of season in order to look for clues to clear her older brother of suspicion in a 10-year-old murder case. She teams up with her classmate Masaki Maki, who was in a coma for eight years, and her brother, who uses a robot to communicate to them from his zashikirō (Edo period-style room for confining criminals). But Yūko has a true form...