On Earth, vampires are not only real but also dangerous. Although humanity has managed to keep them under control and even deprived them of the night as their natural habitat, some have adapted. Hesperides, a relatively new breed of vampires, have adapted over hundreds of years to be able to go outside during dusk, when sunlight is at its weakest, and feast on humans. Aburaya Shiro, a high school student, lives in a town where there has not been a vampire attack in years, but adults keep warning them against going outside at dusk. Shiro and his classmates take this warning lightly and head out at dusk, only to find out that one of their classmates, whom they thought they knew well, turns out to be a Hesperides. With all his classmates violently murdered, the only way Shiro was able to survive was with the help of a different classmate, Ichijoji Eruka, who doesn't seem to be human herself.