Unable to find any stimulation in his daytime life, Kou Yamori, a young middle school student, has become an insomniac and wanders the city in the dead of night, like a castaway in search of a landing place. During one of these desperate walks he meets Nazuna Nanakusa, a slightly strange girl and also a night owl, who helps Kou to fully embrace the nightlife. What he doesn't know yet is that she loves to wander around after dark because she is... a vampire! Is it only the lust for his blood that drives Nazuna, night after night, to meet Kou, or is it perhaps something else?