Great power does not often fall into the hands of the responsible.

Kari never wanted her powers. When she was surrounded and faced with the gnashing jaws of horrifying monsters, a voice offered her a chance to save herself and her best friend Makina. Once she slipped on the gem-studded ring dropped before her, the Apocalypse System activated, transforming her into and granting all the powers of a magical girl. Her outfit, however, looked nothing like the cute ones others wear. Her robes appeared as though stained with blood and her skills were all brutalizing attacks.

She didn't want this at all, but the system left her with a cryptic message that couldn't be ignored...

Apocalypse is coming, Kari Tachibana.