Thousands of years ago, the world was plunged into Chaos, ruled by demons. Death reigned supreme, and humanity's future seemed hopelessly bleak. The demons-creatures of immeasurable power-were led by the Demon King, the most powerful entity in all existence.
Yet amid this despair, a man, insignificant among the masses, stood against the tyranny of the monsters from the void. That tiny spark of rebellion managed to unite humanity's scattered hearts into a colossal force. Together, they formed a storm so devastating that the demons were driven back and imprisoned in their original realm, sealed away-what was hoped to be-for eternity.
To maintain this seal, a dark ritual was established: each year, a one-year-old child had to be sacrificed on the demons' altar, in every city of the Chūbu region of Japan. This ritual, passed down from generation to generation, continues to this day, fueled by the fear that the demons might one day return, bringing terror and death back to Earth.
However, over time, the tradition changed. The children are no longer killed, but merely abandoned on the altars-alive. On that night, unbeknownst to anyone, it was not the portal to the void that was sealed... but the fate of all humanity itself.