In the future, Earth has been ravaged by nuclear war. Survivors are captured by an evil alien race of the Galran Empire led by the ruthless King Daibazaal to work as slaves or fight in a deadly arena. Five captured Earthlings: the fearless Captain Akira “Chief” Kogane, the silent Takashi “Quiet” Shirogane, the strong Tsuyoshi “Hothead” Seidou, the reckless Isamu “Moody” Kurogane and the small but crafty Hiroshi “Shorty” Suzuishi, will attempt to escape the dungeons of Castle Galra before they are again forced to fight in the arena or worse, turned into massive Beastmen monsters.