Fiancé wa Monster!?

Hitomi Miku goes to live in a mysterious house, where she meets Rauto, the young and sexy master of the house. There, she discovers that the house is full of monsters! Rauto gives her a special necklace, and she suddenly transforms and knocks out an evil monster who had possessed a girl! What's going on? Becoming Rauto's maid and fiancé? "I'll knock out everyone's heart."