A vampire named Saya, who is part of covert government agency that hunts and destroys demons in a post-WWII Japan, is inserted in a military school to discover which one of her classmates is a demon in disguise.

In 1970, the four hundred year-old skilled samurai Saya is sent to the Kanto High School in an American military base in Tokyo by the Council, a secret society that has been hunting vampires for centuries. Saya has the appearance of a teenager but is the tormented half-breed creature with the soul of her human father and the powers and need of blood of her vampire mother. She is obsessed to face the powerful demon Onigen that killed her father