Kurogane Naoto was a mostly ordinary high schooler who lived a peaceful life with his childhood friend Hayami Haruka. What wasn't ordinary with Naoto is that his right eye is a little special, it possesses a special ability, "Hunter's Eye", that make it possible for Naoto to see other people's Life Force in numerical values.

But his ordinary days ended when he met a girl with such high Life Force that she couldn't possibly be human. The girl introduced herself as Raquel Alucard, a vampire. She ordered him to get the hold of the Azure.

And so Naoto was dragged into a bloody battle surrounding the Azure.