Yousei Ningyo Shoujo Kurumi

Whenever Kurumi is sad and wishes she was more brave, she looks at her fairy tale book. One day, a "Coppelia" called Chestnut comes out of her book, saying she came from the fairy world through a portal created by Kurumi's strong desire. But now that Kurumi has a Coppelia, she's expected to fight others in battles where the loser ends up undressed.