The protagonist is a vampire named Camus Cain, a descendant of Cain. In order to track down the beast-like vampire Leonard Seta who killed his mother's family 170 years ago, he met the Japanese Masaki Kitagawa who was an intern of the National Security Agency. Due to long-term contact, Camus developed a different feeling for Kitagawa, but he always told himself that it was just the other person's blood that attracted him more, while ignoring the nature of the relationship between the two.