SERVAMP

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. <em class=de-emphasized>(from manga)</em>

Synopsis from Anime News Network