The Ultimate Gundam was created in the space colony of Neo-Japan by Dr. Raizo Kasshu and his eldest son, Kyoji Kasshu, with the noble purpose of healing the planet Earth through the use of nanomachines. The Ultimate Gundam's nano-technology was incredible, capable of self-evolution, self-regeneration, and self-replication which would heal the world after being ravaged by so many years of war and misuse. However, shortly before the 13th Gundam Fights were scheduled to begin in the year Future Century 60, the Ultimate Gundam would be stolen, and Mikino Kasshu, Raizo's wife and Kyoji's mother, would be murdered. The alleged culprit was none other than Kyoji Kasshu, who fled to Earth with the Ultimate Gundam with the Neo-Japanese military in hot pursuit. The Ultimate Gundam was severely damaged by the atmospheric re-entry, and it crash landed on Earth.
After it crash landed, the Ultimate Gundam's systems malfunctioned, and when it begin to repair the damage it had sustained, it started to change. It would evolve into the monstrous Devil Gundam, and it set about accomplishing its goal of healing the world. However, as the Devil Gundam saw it, the problem with the world was humanity, and eliminating mankind became its number one priority. As for Kyoji, he had become integrated with the Devil Gundam and became its core life unit. Major Ulube Ishikawa was soon sent to re-capture the Devil Gundam at the crash site, but the Devil Gundam easily overpowered the mobile suit forces sent after it, leaving Ulube as the only survivor.
For his part in creating the Devil Gundam, Dr. Raizo Kasshu was sentenced to be cryogenically frozen. Domon Kasshu, the younger son of Dr. Kasshu, who was away training to be a master martial artist when the theft of the Ultimate Gundam occurred, was forced to become the official Gundam Fighter for the nation of Neo-Japan. Domon was told that he must both win the Gundam Fight Tournament and recover the Devil Gundam. If Domon was able to do both, his father's sentence would be overturned and he would be unfrozen, but if he failed his father would stay frozen forever. Infuriated at his brother for murdering his mother, stealing the Ultimate Gundam, and leaving his father to an icy prison, Domon set out to Earth at the start of the 13th Gundam Fight with a picture of his brother Kyoji in hand, asking everyone he meets if they have seen him
At the urging of Neo-Germany Gundam Fighter Schwartz Bruder, Domon Kasshu went to South America to train in the Guyana Highlands, the very spot where Master Asia had trained him to be a martial artist. However, the Devil Gundam and Master Asia followed Domon and attacked with massive hordes of Death Army variations and Gundam Heads, devastating the Guyana Highlands. Domon's Shining Gundam was able to defeat the Devil Gundam and its hordes, but in the process, it was severely damaged by Master Asia. But when all seemed lost, Domon's partner Rain Mikamura sent Domon the new GF13-017NJII God Gundam which Domon used to defeat Master Asia and flee the Guyana Highlands.
The curse of the Devil Gundam would not be ended that easily. Under the consultations of Master Asia, Wong Yung Fat, the leader of Neo-Hong Kong, had the Devil Gundam's remains transferred to Hong Kong, the location of the Gundam Fight Finals. Wong believed he could use the Devil Gundam to make his rule of the Earth more permanent; however, the Devil Gundam was badly damaged, and worst of all, Kyoji Kasshu was on the brink of death and almost worthless as the Devil Gundam's core life unit. Wong set out to find a way to try and replace Kyoji, and his scientists discovered that a male was not as suited to be the core life unit as a female, the givers of life. Wong schemed to make Allenby Beardsley, the fighter for Neo-Sweden, the Devil Gundam's new core life unit. Master Asia, on the other hand, believed that Domon Kasshu, the most powerful of all of the fighters, should be the new Core Unit.
As the final Battle Royale, the last fight of the Gundam Fight Tournament, began, the Devil Gundam was set loose on Lantao Island. It was here that Domon learned the truth. The Neo-Japanese military, lead by Ulube, were the ones who had attempted to steal the Ultimate Gundam and the ones who murdered Domon and Kyoji's mother, and they froze Dr. Kasshu to keep this a secret. Kyoji took the Ultimate Gundam to prevent the military from stealing it. Schwartz Bruder was actually a clone of Domon's brother Kyoji that was created through the use of DG Cells. Kyoji tried to use Schwartz to lead Domon to the Devil Gundam so that he would kill Kyoji and destroy the Devil Gundam. Armed with the knowledge that he had been lied to, Domon was forced to grant his brother's pleas for a mercy killing and used the Sekiha Tenkyoken against his brother and his clone, rendering the Devil Gundam useless.
Domon was crowned the winner of the Gundam Fights, bringing victory home to Neo-Japan, but Ulube recovered what little remained of the Devil Gundam and transported it to his home colony of Neo-Japan. He followed Wong's research and chose a woman to be the new core life unit: Domon's partner Rain Mikamura. The Devil Gundam grew more powerful than ever, growing at an alarming rate, and soon it had absorbed the entire colony of Neo-Japan, becoming the Colony Devil Gundam. This mode was vastly unlike all previous evolutions, as most of its body structure was composed of gigantic Gundam heads that were clumped together with a drastically different primary head design. Ulube, driven mad with power, declared that he would be the Earth's permanent ruler, and the other nations responded by declaring war on Neo-Japan. As the armies of the world fought the Colony Devil Gundam, the Shuffle Alliance infiltrated the interior of the colony to try and stop the Devil Gundam at its source. Ulube, now little more than an avatar to allow the Devil Gundam to talk to its human foes, attempted to stop them by transforming the power generator into the monstrous chimera Grand Master Gundam, a gigantic fusion of the Devil Gundam's Four Kings. Ulube and his new Gundam were defeated by the Shuffle Alliance's team attack (Bakunetsu Shuffle Doumei Ken/Erupting Shuffle Alliance Attack), and Ulube turned to dust. While his allies stood behind to hold off the regenerating Grand Master Gundam, Domon ventured deeper into the colony.