From a young age, Yakumo's mother told him two things. One was that his father was a vampire, and the other was that when his father neared death, a messenger would come for him. Yakumo didn't believe her.
However, after his mother's death, a black dog that could speak appeared before him, and he learned that the things she said were true. The black dog told Yakumo that he was the son of the king of the vampire world, therefore a candidate to succeed him, and that he had become his guardian.
Yakumo is forced to take part in the "race for succession", with his mysterious and sinister guardian by his side. A life-or-death battle begins, where losing means losing his life!