Köinzell, un joven espadachín que empuña la mortífera espada negra, se enfrenta a rumores de derramamiento de sangre. Perseguido por las Lanzas Traidoras, intenta descubrir la verdad tras su búsqueda entre los cadáveres de sus enemigos.

This is a tale about humans and vampires. Taishou Romantism: the blooming era. Ladies and gentlemen chat in cafes about the avant-garde and other European trends. But this tranquil lifestyle is destroyed, when vampires start to randomly attack the living. The government of Japan has known about their existence for some time now, but now that these creatures start their hunt against the humanity, the Japanese government creates "Code Zero," a corps that is created to get rid of the bloodthirsty undead.