Ji-yeon, a high school student raised in an orphanage, takes a job at an illegal slaughterhouse to survive. There, she encounters a mysterious girl who has been raised in isolation, treated as a "monster." Ji-yeon named her Eugene, and the two form an intense bond, becoming everything to each other. But when Eugene kills her abusive father and awakens as a vampire, the girls find themselves hunted by those who seek to destroy "demons." Abandoned by the world, they now fight to protect each other—no matter what it takes.