Kaito Tanaka, an unremarkable Japanese game developer, dies a meaningless, regretful death after saving his colleagues in a bus crash. Instead of an afterlife, he's processed by a cold, bureaucratic "System" and forcibly reincarnated into a high-fantasy world on EXTREME NIGHTMARE difficulty, with no cheats, no status window, and no foreknowledge.
He is reborn as Zyphron, the eighth and youngest child of House Theodore, a powerful and chillingly enigmatic noble family in a human empire that exists in a fragile, magically-enforced cold war against ancient elder races (dragons, elves, etc.). Trapped in the gilded cage of his nursery, Kaito must use his only weapons—a modern analytical mind, a talent for narrative understanding, and sheer relentless discipline—to survive. He secretly trains his infant body to superhuman levels, teaches himself the alien language and magic system (Aether), and uncovers his family's darkest secrets and the world's brutal history through clandestine exploration and intellectual theft.
As he grows, he must navigate the lethal politics of his family, where every sibling is a potential threat and his father's smile never reaches his eyes, all while preparing for the true "Nightmare": a world where humans are the disruptive, hated newcomers, where demigods once walked, and where the peace is a thin barrier away from total species war. This is a story about forging one's own fate with intelligence and grit in a universe designed to break the ordinary.