Hakushaku to Yousei Namida no Himitsu wo Oshiete

Fairy doctor Lydia Carlton has returned to her hometown in Scotland for a well-earned rest. Taking an extended Christmas vacation was a fine excuse, but the truth is that she feared falling in love with her employer and would-be fiancé, Edgar Ashenbert, the Earl of Ibrazel. The history of his title is a complex affair, and when she hears a mysterious rumor about the earl’s forefather, Lydia heads to the Isle of Mannan to investigate. Meanwhile, a strange girl appears before Paul, Edgar’s artist friend in London, and it soon transpires that she isn’t exactly human... (Source: J-Novel Club)