Seventeen-year-old Chiyuki Matsuoka was born with heart problems, and her doctors say she won't live to see the next snow. Toya is an 18-year-old vampire who hates blood and refuses to make the traditional partnership with a human, whose life-giving blood would keep them both alive for a thousand years.

Now that her bond with Toya has healed her heart, Chiyuki wants to live her life to the fullest. What she doesn't know is that Toya has refused to make the full partnership with her. He doesn't want to doom her to a thousand years of life. Chiyuki swore to Toya that she would never leave him alone, but is that a promise she'll be able to keep?