By the 21st century Earth had become uninhabitable, prompting mass exodus to Planet Zi, the native realm of metallic beings called Zoids. Decades later Zi itself nears collapse, and its residents embark on a return voyage to Earth. In an effort to restore Earth's livability, the refugees devise a plan dubbed "Zi‑Forming." The initiative collapses, leaving Earth in chaos: overrun by Zoids and battered by erratic weather, the survivors endure harsh conditions. Imperial and Republic outposts scour for hidden Zoids beneath the planet to strengthen their forces. The narrative centers on second‑generation Earthlings Leo Conrad and Buzz Cunningham, who encounter Sally Land while she escapes the Empire"s grasp.
