Medusa

Medusa (メデューサ?) is the leader of KMM Gang, and a very powerful Tower Witch that is after Honoka Takamiya for the White Princess Evermilion who was sealed inside of him for an unknown reason. It is also unknown why Medusa is after her but it is assumed that she wants to take the white princess' power for herself.

(Source: Witchcraft Works Fandom)