Forgotten (Black butler)

Snow. A girl who only remembers her name and has lost her memories. She has long silver hair, and red eyes. She is discovered by the Earl Phantomhive at the woods behind his garden with his butler Sebastian. And to be taken in as a maid. Snow appears that Sebastian is familiar to her. Since snow looks like his childhood sweet heart. As days go by, she starts to remember some of her memories. But also. Other demons want her as well. Without further explanation. Why is that? Just who is Snow anyway...?