This is a world built on prehistoric ruins. No one knows how far the lost civilization of the old century has developed. There seems to be a fault in history—after the old civilization disappeared for thousands of years, the new human beings emerged out of thin air. Appeared on the land that was once swept by the catastrophe, but they are like primitive people who have just completed evolution. They have nothing but animal instincts. The wheel of time is slowly rolling, and the new human civilization is gradually Germination in the embers, the process of history repeats itself, from the beginning of slash-and-burn farming, to the roar of steam machinery resounding in the sky... Humans, a race that almost disappeared from the world, finally became the master of the world again. Until that day comes , the most prosperous metropolis on the mainland was completely destroyed overnight by a beam of light that fell from the sky, and what was replaced was a piece of ruins called the second quarantine area...