The axis of Planet Zi moved suddenly, and it caused the disasters. The plain was split, the tropical islands moved to the polar, the seabed became mountains, sleeping volcano erupted, and the sky was covered with thick grey clouds. The cities were destroyed, and they were swallowed into the earth or seas. People were helpless against the catastrophe, and their civilizations were ruined.
Several thousands years have passed since then. The new civilization was rebuilt on the earth. The disaster was handed down as myth called "The Wrath of God". The few people survived during the disaster made their own civilization.
However, the legacy from the previous civilization exists around the world. They are huge facilities, "Generator". They are scatted around and still working. And, biomechanics, "ZOID". They are over technologies of the previous civilizations, and sometimes found as relics.
Some of ZIOD can be operated by people, and they use ZOID to develop their societies. Then, a job called "ZOID finder" is born. In addition, those who can manipulate ZOID is called "ZOID rider", and they are respected by people. However, ZOID is not used only for the peaceful purpose. There appears a country where they want to use them as arms. It is Digard.
It is a story about people who are undauntedly fighting against Digard which try to rule the world by arms.