Dirappen are robot soldier units from the planet Darptha. Dirappen, masquerading as harmless robotic servants, are sold off in droves to planets across the galaxy, waiting until a sufficient population of Dirappen have been shipped to any single planet before attempting a full-scale invasion.
One day, however, on the planet of Hoska, a lone Dirappen was assailed by its owner, none other than the ruler of the Hoskanites, the Magician Gabriel. In response, the lone Dirappen enters "attack mode", only to be quickly halted; and Gabriel, now furious with the threat of the Dirappen, rushes off with his fellow Hoskanites to invade the Dirappen manufacturing world of Darptha.
Through hostile takeover, the Hoskanites swiftly destroy all Dirappen on Darptha, all except for one.
As the last Dirappen remaining, Dirappen Unit D6-4 must overcome impossible odds in order to reestablish Darptha to its full glory.