In the original storyline as aired in Japan, Dairugger XV was simply an exploration robot, as well as an intended peace-keeping force. The Earth is in a time of prosperity. The president of the Terran League (the "Galaxy Alliance" in Voltron) launches a mission to explore beyond the galaxy. After commencing its mission of exploration, the starship Rugger-Guard is attacked by a ship of the Galbeston Empire. Dairugger, the super robot, is deployed in order to defend the Earth. It is somewhat by fate that they must help the people of Galbeston find a new planet before it explodes, and liberate it from its despotic Emperor. In the Japanese version, it does not have anything to do with King of the Beasts GoLion, as opposed to the U.S. version, Voltron: Defender of the Universe. There are three assault team units: Land, Air, and Sea. There are a total of 15 parts referred to as "Rugger," which can combine together to form the super-robot Dairugger. The design of the 15 separate Rugger units came from the sport of rugby, since 15 players are required to form a rugby union. The U.S. version would rename the "Galbeston Empire" to "Drule Empire," along with editing a fair amount of violence and sexual content to keep the show safe for general audience broadcast.

Twenty years into the future, a city now called "Tokyo" has developed into one of the few world-class high-tech centers, "Tokyo City." The main character, Ken Kanzaki, is a young investigator assigned to the criminal investigation section of the Metropolital Police. He is one of the finest sharp shooters in the Police.One day, Ken is ordered to provide security for a party held by for "Zaizen Konzern," a world-class plutocracy. All of a sudden, spector robots appear and distrupt the party. Zaizen, a commander-in-chief, is killed and both Ken and Jun. Zaizen's son,are fatally injured by the robots. Two of the party's guests, an auto-racer, Ryo Aguri,and a wresler, Go Goda, also receive serious injuries. Three severely injured young men are operated upon by scientists from the Metropolitan Police. Several days later, a robot corp led by a mysterious organization called "Ido" appears in the floating-town of the Tokyo Bay. But the Police and the Army have no effective strategies to contain them. At that moment, three young men attired in mechanical suits enter. They are the very three young men, Ken, Ryo and Go, who have been turned into the cyborg investigators through the operation. They call themselves "Armored Police Metal Jacks". "Metal Jacks," dazzlingly switching from "Jack Suits" to "Jack Armors," completely demolish the robot corp and achieve victory, thus signals the beginning of the battle between the high-tech criminals and "Metal Jacks" with a futuristic "Tokyo City" in the background.

As the sole survivor from a squad that was sacrificed and hung out as scapegoats for embezzlement of military resources at the end of the 100 years war, Mellowlink Arity is out for revenge. Carrying the dogtags of his deceased comrades and armed with a dated anti AT rifle, he swears to hunt down and exact revenge on the corrupt officers that betrayed his squad, and maybe even uncover the truth behind the plot as well.

A.D. 2087 - the United Lunar Empire Giganos wages war on the Earth Federation Military to take control of the planet and establish a "rebirth" of the human race. During an invasion of a colony by Giganos' forces, three civilian men stumble upon a trio of top-secret Metal Armor units called "Dragonars" and pilot them to combat the enemy forces.