The Masked Man! What Is His True Identity?

One of Maron's Friends has been possessed by a demon. The demon changes her friends personality and at first Maron thinks it has changed for the better, but then his personality turns cold and mean. Jeanne sends a warning, but Sinbad ends up trying to checkmate the painting they think is possessing him... but he's actually possessed by a book and Jeanne takes the "checkmate" for herself.