Within Akanegasaki Middle School, there is a spooky legend going around. It tells of a bell that tolls when young girls walk alone at night, and a woman in a long coat magically appears out of nowhere. This woman is known only as the Ripper, and after asking for the girl's name, she brutally attacks them with a blade.
Haruka Kanade, Arisa Narumi, Chisato Shion, and Matsuri Hinata have all heard the rumors of the Ripper, but they know the truth behind the tale. It originates from a series of gruesome murders in a nearby town. Unlike most others who are simply scared, the girls believe they can stop the horrific crimes. They have made a promise to a cat-like entity named Kyuubey, who has given them supernatural abilities. One night, they venture out on patrol and come face-to-face with the Ripper. However, things take a dark turn when they realize she too is a magical girl.