One Hell of an Idiot

Serien Blackheaven is the princess of the Demon Realm and is supposed to get married in 8 months, but then she heard that her fiance had disappeared to the human world and so she decided to search for him there, along the way of her search, she bumped into Sebastian Michealis, a butler of the Earl Ceil Phantomhive who also is a demon, she had then began to work for Ciel as a bodyguard and maid in exchange of letting her stay in his mansion so she can search for the fiance that she never met or know.
Sebastian however already knew who Serien is talking about and he too decided to stay quite about it and not tell her for it is her job to find out her missing fiance, but what will happen to Sebastian's plan if his Pokerface rival, Claude Faustus and his "master", Alois Trancy come into the scene? Will Sebastian tell Serien who he really is in time or will he just be a stupid idiot who stays in the shadows and let Claude take Serien away?