The premise hits hard in the first episode and never stops twisting: you watch Kai lose everything he fought for, then realize the world he's fighting to restore might be worse than the one that erased him. The show burns through conceptual fuel faster than it can explain itself, which means you're constantly one step behind, solving the mystery of what reality actually is while Kai is already three moves ahead. It's messy and the animation won't impress anyone, but the core idea, that some heroes only exist in worlds that no longer need them, sticks to your ribs in a way clean storytelling never could.

Long ago, humanity won a great war against rival races thanks to the hero Sid, who sealed its enemies away in pyramids. Kai is one of the conscripts assigned to watch over those tombs. Then, on an ordinary day spent with his friend Jeanne, the world is suddenly overwritten. In the new reality, humanity lost the war without Sid, demons rule the land, and the surviving humans live in hiding. Kai's existence has been wiped out, and everyone he knows, including Jeanne, now a resistance leader, has forgotten him. While searching for traces of his old world, he meets Rinne, a mysterious girl imprisoned in a pyramid, and frees her after inheriting Sid's legendary sword. Joining forces with Rinne and Jeanne, Kai sets out to break humanity free of demonic rule and learn what caused reality to change.