the stories is about a human girl(CHAE YOUNG) that had been raise and lived with vampire family LEE JIN KI'S aka onew.

for your information Lee Chae Young's parents and Lee Jin ki's parents were friend ...After Lee Chae Young parents died when they were on mission(both of her parents work as vampire slayer).

because lee jin ki the only son (cause vampire can give birth only one child) so, his parents decided took her as her own daugther and their friend sake.