The wasteland after nuclear winter is depleted of resources. Leon, the former federal ace mecha pilot, drives a rusty old mecha code-named "Old Dog" and makes a living by scavenging in the wilderness. One day, he discovered a starship signal transmitter buried underground. The signal pointed to mankind's last hope - the "Ark" colony located in a distant galaxy. He must repair the mecha, travel through a wasteland filled with mutant monsters and hostile predator groups, and activate ancient starships, but his biggest enemy is time, because a super radiation storm that is enough to annihilate the continent is forming.
