Aster, the Living Solar System

Sadalla. Once upon a time, this was the name of a saiyan who dominated Universe Seven. But before that, he was known as Son Tao. One of many "legacies", he was born about two hundred years after the legends Son Goku and Vegeta had their final fateful clash in a solar system far beyond Earth.

Legacies were the colloquial term for people born with saiyan heritage, but none of the qualities that had defined the original saiyans and hybrid saiyans. The only this Son Tao had was a far greater potential and talent for fighting than others, but while that allowed him to get into his family's Son Martial Arts Academy, it didn't compare at all to his ancestors' ability to transform into Super Saiyans and even Super Saiyan God.

Son Tao dreamed of nothing more than being able access these states. He wanted to push himself beyond the limits that people had accepted. He had hope, too. His great grandfather was Goku Jr., who had been able to transform, and he was also a descendant of Vegeta Jr. His bloodline purity was the highest since their generation, and Son Tao spent every waking moment of his desperately training in his family's gravity chamber, and the ones at his school, until finally, at the age of twenty, he succeeded. He channeled all of his willpower into reaching the Super Saiyan form, and he did it.

What he also succeeded at though, was being the first person to kill themselves by transforming. He had overtaxed his body to such a high degree that the surge of power from transforming instead ended up ripping him apart. Thus, Son Tao was no more.

Son Tao's soul was taken to King Yemma, the guardian of the afterlife, and Son Tao was deemed a neutral soul, not possessing any strong karmic ties in either the evil realm of Hell, or the heavenly realm of Otherworld. As a neutral soul then, his natural path was to simply be reincarnated without memories. Son Tao's will was strong though, and not easily erased.

King Yemma asked King Kai, his boss, to help him. King Kai, however, didn't know what to do either. King Kai could indeed erase Son Tao's memories, but doing so felt like a betrayal of Goku and Vegeta, whom had likewise given their lives to the same drive as Son Tao. Son Tao also possessed a lot of potential as a fighter. Had he trained at a more modest pace, he likely would have become a Super Saiyan without needing to kill himself. With his own mind in turmoil over this, King Kai defaulted to his own boss, the Supreme Kai known as Shin.

Shin was just as confused as King Kai. He couldn't just use the dragon balls, as they had been deactivated long ago as a precaution against beings like Frieza and Morro, who had attempted to use their power to cause untold calamities upon the multiverse. Another being, Zamasu, had attempted to do the same with the Super Dragon Balls, leading to them also being held by the Omni King Zeno as a precaution against such acts. Shin wasn't willing to ask Zeno to use them just for a single saiyan child, even if he was the descendant of Goku.

Ultimately, Shin decided that, even though it was a shame, the best scenario was simply to reincarnate Son Tao with his memories intact. It was the least they could do out of respect for Goku and Vegeta. Like many things in Shin's life, this would prove to be a hilariously dumb mistake.

You see, the reincarnation magic used by King Yemma works by placing a purified soul into a new baby body. The magic isn't designed to work on souls with memories intact. Nothing like this had ever happened before because the Kais had never been so involved in the fate of a mere mortal. When combined with Son Tao's willpower, the magic backfired, destroying Son Tao's soul completely.

As you could guess though, that wasn't the full story. While dead in this timeline, Son Tao's soul entered a new timeline, in a new continuity. Creating a new timeline was as simple as attempting to travel backwards or forwards in time. Creating a new continuity though required fundamentally changing the fate of the multiverse in multiple timeline at once. Son Tao's soul did this as it travelled not only into a new body, but into a new time. To planet Plant, in Age 670.