Hakushaku to yousei, book 4: Koibito wa yûreiMizue Tani2005

Lydia, a girl who can communicate with fairies, is a Fairy Doctor hired by the Earl Edgar, a rake with a complicated past. For certain reasons, the two of them have fabricated an engagement with each other, but Edgar is a lascivious man so much that he gladdens the gossip papers and Lydia is always swayed around by him. One night, a spiritualist who meets Edgar discloses to him that the two of them are acquainted and announces that she will be doing a ghost resurrection. Knowing that it's a trap set up by his nemesis Prince, he still attends the gathering, but the spiritualist who appeared before Edgar looks exactly like his dead friend Ermine...!?