Chiyuki Matsuoka's given name literally means "thousand snow," and it embodies her parents' wish for her to witness the first snowfall of the year perennially. This wish is exceedingly optimistic due to Chiyuki's heart condition, which increases the risk of seizures and decreases her life expectancy. The doctor who presided over her birth said she would be lucky to live 15 years.
Chiyuki is 17 years old when she meets the unlikely vampire Toya Kano. He claims to hate blood, and he refuses to find a human partner with whom to share the rest of his life. Toya is 18 now, but if he took blood continually from a partner, then they both might live to be a thousand years old.
Chiyuki immediately volunteers to be Toya's partner, but he shoves her away in disgust, inadvertently learning of her poor health when she starts to spasm. Toya treats Chiyuki more kindly after that, but still refuses to drink her blood. She begins to suspect that there is a different reason why he keeps turning her down, but will she live long enough to discover the truth?