A succubus – a demon who prays on human sensual energy - takes over Allison, a university freshman. Soon she learns about the existence of a mystery organization of demon hunters and discovers that a locket left to her by her late grandma is not just a piece of jewelry but a powerful artifact. Now she has to untangle a web of mysterious intrigues in order to find out why she is the one who is hunted by demons. The ordinary girl has to deal with Scarlet, a handsome and irrepressible demon lover, and Gray – a cunning, seductive, malicious and heartless sadistic incubus. But is Allison as ordinary as she thinks she is? Who was her Grandma? And who is Allison herself, really?