In a desperate measure to combat the overpopulation of Earth, scientists work to create an artificial planet named Altile, named after the scientist who designed it. During the construction of Altile, humanity has become united and peaceful. During this new era of prosperity, Earth decommissions the RoboWarriors, a force of heavily armed half-man half-robot war vehicles. But from another dimension, aliens calling themselves the Xantho Empire and lead by the being Xur invade planet Altile and terraform it for their own uses. The survivors of Altile send out a distress call to Earth. Receiving this message, the people of Earth quickly activate the latest and most powerful of the RoboWarriors, a model known as ZED (Z-Type Earth Defense) and send it at top speed to Altile.