As a result of the great war that took place in the past, the earth was so heavily polluted that it became uninhabitable. The human population gradually declined. The survivors used the nanotechnology accumulated during the war to build a huge city-state with low pollution levels. People lived in this city, gradually cleaning it of pollution, and the population began to recover.

As the population grew, new cities began to be built in other places, and records of the war and technologies that hindered the recovery of humanity were sealed and destroyed. In the hope that the people of the future would not repeat the same mistakes.

Time passed. And everyone forgot about the great war.

At first glance, everyone lived peacefully, but in the shadows of the city, chaos and turmoil began to brew.

To combat dissent, guards were created to suppress any such actions and maintain peace in the city.

The Administration's Relic Control Department. Young ace Koga and his partner Ixus fought criminals day and night.