I met a Mahou Shoujo; and so began my story-- "Then I will become a Mahou Shoujo!" In order to save Hoshi Karen, the Mahou Shoujo who had protected her even while being pursued by tanks. Kokone, who was entrusted with Karen's Grimoire, decides to become that which is acknowledged as a "Calamity" by the world... A Mahou Shoujo!