Seiken Gakuin no Maken Tsukai

Seiken Gakuin no Makentsukai unfolds after the long war against the forces of evil reaches its final stage, with Leonis Death Magnus, the Undead King and last surviving Dark Lord, choosing to seal himself underground and wait a thousand years for a chance to rebuild his demonic army. When Leonis awakens in a very different era, the world has forgotten the old war. Magical devices now stand where sorcery once ruled, and humanity relies on Holy Swords—special powers manifested as weapons—to fight the monstrous Voids that threaten civilization. Reborn as a 10-year-old human boy, Leonis emerges into this strange new age with the same ambition he had before: to take over the world. His path changes when he meets Riselia Ray Crystalia, a dutiful girl who discovers the ruins of his hibernation chamber and mistakes his situation for amnesia. She brings him into Excalibur Academy, where students train to battle the Voids. While Leonis struggles to understand this unfamiliar society, he must hide his true nature, navigate his connection with Riselia, and decide how to pursue his goal of restoring his power in a world that no longer remembers the Dark Lords.