Ao no Fuuin

After moving to a new city, Soko inexplicably begins to feel sick. At school, as beautiful as she is, a lot of guys start to bother her, especially Kashi. When Kashi tries to rape her, however, he disappears, and a few days later another man shows up posing as Kashi. The only thing is, though he looks nothing like Kashi, only Soko can tell he's a fake! The new man tells her he's Akira the Byakko, from the family of the West. Because she's the reincarnation of Souryo from the family of the East, the queen of the demons, she must be destroyed. He's the only one who can kill her, and it's his duty to do so. Is she really a monster? Why does she have human memories? Why does she have to die? Will she be able to change her destiny and live on?

(Source: Storm in Heaven)