The events take place in the year 2222. Much time has passed since the mysterious Tears of the New Moon rain destroyed almost all of humanity. The toxic rain created horrifying creatures that feed on humans, and they fled. In order to preserve their lives, people built a shelter underground called Amasia. In this recently created city, they encounter an artificial intelligence named Mag. Thus begins the story of how humans and artificial intelligence try to coexist in a new world.