The earth is ruled by the Black Witch. The Black Witch was sealed in the moon and can only be judged once a decade on the night of Hexennacht. The ones who can fight the Black Witch are the chosen magical girls who have won their battles. Horinouchi Mitsuru, the Eastern Japan representative who aims to be the strongest, happens across a girl with strange power who says her name is Kagami Kagami. The girls "clash"! To save the world with their own power!!