A young woman on a train eyes a nervous man. In a flash, he is chased down the train and the young woman slices him in half. She is Saya (小夜; Jun Ji-hyun), a four-hundred-year-old skilled Dhampir samurai who hunts vampires. Raised by a man named Kato (Yasuaki Kurata), she works loosely with an organisation known as "The Council", a secret society that has been hunting vampires for centuries. Saya's motivation goes beyond duty; she wants revenge; Onigen (Koyuki), the oldest of the vampires, murdered her father. For her next mission, she goes undercover as a student at Kanto High School on Yokota Air Base near Tokyo, Japan.