Fiance wa Monster!?

Fiance wa Monster!? summary: 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 possesses a girl! What's going on? Becoming Rauto's maid and fiancé? "I'll knock out everyone's heart."