There’s an orphanage which trains its charges to be weapons of war, assassins specialised in magic. At this school, Shiina has been having a difficult time coping with her roommate’s death. She completely ignores rumours, including that of a student named Mimi, who is thought to be even stronger than the teachers. While taking a break, she encounters an overly cheerful young girl covered in blood. They chat for a while before the girl is hauled away by the school nurse. Shiina thought that they wouldn’t meet again, but the next day, the girl transfers into her class and cheerfully introduces herself as Mimi.