The people of the earth live in a society where vampires are not only real, but also dangerous. Although humanity could keep them under control and even take away their night as a natural habitat of vampires, some of them were adapted. Heperdis, relatively new vampire races, adapted for hundreds of years so that they can go outside at dusk when sunlight is weaker, and enjoy people. Aburay Shiro, a schoolboy, lives in the city where there was no vampire attack for many years, but adults warn them to get out at dusk. Shiro and his classmates perceive this warning lightly and leaving at dusk only to discover that one of their classmates they thought they knew well, turns out to be hesperide. With all his comrades, cruelly killed.