It is the early 21st century, and mankind is doomed. Due to a mysterious virus that steals the essence of human life, humanity has been pushed to the brink of extinction with only one hope for salvation: the blood of a vampire. Vampires have closely guarded the key to curing the virus for several years, which has led to an immense rift between them and humans and the world's descension into chaos. A vampire named Duo, having leaked the secret to saving humanity, is now considered a traitor to his race, and the powerful vampire Zieg is on his trail. However, due to Zieg's sense of duty, his heart is torn: should he kill the man who betrayed his people, or will his personal history with Duo sway him to have a change of heart? The fate of mankind is doomed in the early 21st century due to losing purana, an essence of living force supporting all life forms. Not willing to witness the extinction of mankind, a vampire named Duo disclosed the secret of purana to humans, saving the latter from destruction. However, just like Prometheus in Greek mythology got punished for bringing fire to mankind, Duo is punished for breaking the taboo. The vampire sent to punish him is Zieg, Duos best friend, or, more than the best friend.