Why Does Nobody Remember Me in this World?

"Why has the entire world forgotten me?" Long ago, a devastating war raged across the Earth among five distinct races: Humans, the Demonic Race, the Wild God Race, the Spirit Race, and the Phantom Beast Race. Humanity ultimately emerged victorious thanks to the legendary Prophet Sid, who sealed the four rival races within a massive black pyramid known as the Crypts. Kai serves as one of the dedicated guardians tasked with monitoring these ancient structures, ensuring the seals remain intact. He trains relentlessly, preparing for the inevitable day when the imprisoned races might break free and threaten humanity once more. On what appears to be an ordinary day of watch, reality suddenly distorts before Kai's eyes. A catastrophic phenomenon known as "World Rebirth" is triggered, fundamentally rewriting existence itself. When the distortion fades, Kai finds himself thrust into an entirely altered version of his world. In this new reality, the history he knows has been erased, and not a single person recognizes him or remembers his existence. Yet, despite being completely unknown to everyone around him, Kai retains all of his original memories. Alone in a world that has moved on without him, he must navigate this unfamiliar reality while holding onto the truth that only he remembers.