Mizuki and Karen are Mahou Shoujo Utea. Mahou Shoujo.Utea is a Wizarding Girl who was sent to defeat Majuu (Monster) who came to the World caused many human beings who do evil and created Majuu. Mahou Shoujo Utea was assigned to defeat all Majuu who appeared on Earth and sucked the Soul out of Majuu after being defeated in order to create a Peaceful World.

(Source: Nekopoi and Has Been Translated)