One day, a virus spread throughout the world, and humans over the age of thirteen died one after another. Civilization collapsed, and chaos ensued everywhere. Behind the scenes, vampires, who live far longer than humans, appeared and took the surviving children to underground cities. There, human children were treated as livestock to provide blood, living lives stripped of freedom. Yuuichiro Hyakuya and Mikaela Hyakuya, boys from the Hyakuya Orphanage, were among them. The two planned an escape from the underground with their friends, but were blocked by the vampire noble Ferid Bathory during their flight; only Yuuichiro managed to escape to the surface. Mikaela's fate became unknown, and Yuuichiro etched the sorrow of losing his friends and his hatred for vampires into his heart. Four years later, on the surface, the Japanese Imperial Demon Army was active as an organization opposing the vampires. Yuuichiro joined the Demon Army to fight alongside his comrades and take back Japan. Standing before him were the military power centered on the Hiiragi family, the mysterious Seraph of the End project, and entities that manipulated both humans and vampires. Meanwhile, Mikaela, who had survived underground, was saved by the vampire Krul Tepes and forced to choose the path of living as a vampire. Humans and vampires cannot be simply divided into good and evil; each side has those they want to protect and things they cannot afford to lose. Guren Ichinose of the Demon Army also fights to protect his comrades while becoming entangled in secrets involving the Hiiragi family, vampires, and the Seraph of the End. Guren balances a calm demeanor with a lighthearted attitude, guiding his comrades strictly at times while struggling against his own harsh destiny. Comrades bound by trust gather around him, each heading to the battlefield with different goals. On the surface, the Demon Army and vampires clash violently, while underground, the vampires have established order. However, deeper within the conflict lie research and sorcery continuing from before the world's collapse, human desires, and taboos involving angels. Yuuichiro fights to get Mikaela back, and Guren fights to save his comrades, each with their own convictions. Eventually, the two will face each other again, transcending their positions as enemies. From there, the story advances to the core—not just a war of humans versus vampires, but who is manipulating the world and why the Seraph of the End was created. Everyone makes choices to protect what is precious to them, and sometimes those choices hurt someone else. In a world where despair and betrayal, friendship and sacrifice intersect, the boys and girls continue to fight for their future.