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, Duo's best friend, or, more than the best friend.
Bloodthirst
Great sin
Karma
Gun point
Recollection
Your destiny
False love
Honeymoon
Fatal
Blood feast
Stubborn
Dear
Call It What You Want
BOCCHI THE ROCK!
Baka and Test: Summon the Beasts
Goodbye Again
The Everyday Tales of a Cat God
Minami-ke
Fist of the North Star
Baki the Grappler
KochiKame
Cyborg 009
Eureka Seven
Neon Genesis Evangelion
The Wallflower
Yu-Gi-Oh! Duel Monsters
Ah! My Goddess
Beast Machines: Transformers
Lime-Colored History of War
Moyashimon
The Agatha Christie Hour
Blue Orchestra