In a world decimated by a mysterious virus that wipes out nearly all of humanity, the survivors find themselves at the mercy of powerful vampire aristocrats who emerge from the shadows to claim dominion over the earth. The story follows Yuichiro Hyakuya, a fiercely determined young orphan who vows to annihilate every vampire after witnessing the brutal massacre of his family at the Fuji Sanatorium. Alongside his childhood friend Mikaela, Yuichiro dreams of freedom, but their paths diverge when Mikaela is seemingly lost to the vampires. Years later, Yuichiro joins the Moon Demon Company, a elite military unit wielding cursed demonic weapons, to fight back against their immortal oppressors. However, his quest for vengeance becomes entangled with the mysterious Seraph of the End, a forbidden power that threatens to consume him and alter the fate of humanity itself. Blending dark fantasy, post-apocalyptic action, and supernatural horror, this gripping series explores themes of loyalty, sacrifice, and the monstrous choices made in the name of survival, as Yuichiro and his comrades confront not only their enemies but the demons within themselves.