After the passing of his grandmother who was his only relative, Kazuma returns to a boarding school Meikyou Seigakuen in his hometown. Located in the mountains, it is a quiet school. There he meets his childhood friend Mikoto who he thought had perished in the great fire ten years ago. Likewise, she thought that he had died, so they were happy to be back together once again. However, on the night of every full moon there is a ‘bloodsucking incident’. He noticed that Mikoto acting suspiciously and soon he is wrapped up in events that he does not understand.