Millennium snow

When seventeen-year-old Chiyuki Matsuoka, who will likely die from congenital heart problems before the next snow, meets Toya, an eighteen-year-old vampire who refuses to drink human blood, she tries to convince him to make a partnership with her that would let them both live a thousand years. Although Toya saves her life, he is unwilling to doom Chiyuki to living for a thousand years, so he refuses to make her a full vampire, aware that she will not be able to keep her promise to always be with him.