When a stray black cat named Kuro crosses Mahiru Shirota's path, the high school freshman's life will never be the same again. Kuro is, in fact, no ordinary feline, but a servamp: a servant vampire. While Mahiru's personal philosophy is one of non-intervention, he soon becomes embroiled in an ancient, altogether surreal conflict between vampires and humans.
Natsume Takashi has the ability to see spirits, which he has long kept secret. However, once he inherits a strange book that belonged to his deceased grandmother, Reiko, he discovers the reason why spirits surround him.