One day, a virus spread across the globe, and humans over the age of thirteen died one after another. Civilization collapsed, and chaos reigned 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 grief of losing his friends and his hatred for vampires into his heart. Four years later, on the surface, the Japanese Imperial Demon Army operates as an organization to counter the vampires. Yuuichiro joins the Demon Army and fights alongside his comrades to take back Japan. Standing in his way are the military power centered on the Hiiragi family, the mystery-shrouded Seraph of the End project, and entities that manipulate both humans and vampires. Meanwhile, Mikaela, who survived in the 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, the vampires, and the Seraph of the End. Guren balances a calm demeanor with a lighthearted attitude, sometimes strictly guiding his comrades while struggling against his own harsh fate. 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 an order. However, deeper within the conflict lie research and sorcery continuing from before the world's collapse, human desire, 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 moves toward the core of 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 young boys and girls continue to fight for their future.