The story takes place in the distant future. A mysterious virus has invaded the earth, and all humans over the age of thirteen have become extinct. However, for those children who survived, being alive does not mean luck. The vampires who suddenly appeared became the rulers of the earth, and these children were "raised" as their rations. Yuichiro (voiced by Irino Miyu) and Miguel (voiced by Ono Kensho) are unwilling to bow to fate. In order to resist, Yuichiro joined the Japanese Imperial Demon Army and became a member of the Moon Demon Group. There, Yuichiro met the maverick Hiiragi Shinoa (voiced by Hayami Saori), the kind and weak Saotome Yoichi (voiced by Okamoto Nobuhiko), the gentle Kimitsuki Shikata (voiced by Ishikawa Kaito) and the carefree Sannomiya Mitsuha (voiced by Iguchi Yuka), and the five of them became comrades-in-arms who shared life and death.