No one had really thought too deeply about Yinsen's origins. From appearances, Yinsen and Yoruichi both looked like perfectly ordinary humans, and when they had first met him, Yinsen had merely been a young man in good physical condition.
Although his progress later became astonishingly fast, no one thought much else of it. After all, this was a world where anyone could improve through diligent training; it was only a matter of speed.
Under such circumstances, Yinsen had not needed to make any "adjustments" to his background. But after realizing what his true mission was, he found that some problems had to be resolved in advance.
Neither King Piccolo nor the reincarnated Piccolo required much attention, and all they had to do was wait for the Saiyan invasion. But the later battle on Planet Namek might never happen without a suitable reason.
At their current pace of training, it was entirely possible for them to reach Combat Power levels above ten thousand before the Saiyans invaded. In other words, the Warriors on Earth would not suffer the devastating casualties they had in the original story, nor would they need Planet Namek's Dragon Balls to bring them back to life.
Put another way, because of Yinsen's influence, Krillin and the others in this world had no reason to make a special trip to Planet Namek. They would not encounter Frieza, that cosmic-level archvillain, and naturally would not end up fighting him.
Considering this, Yinsen immediately arranged a new background for himself: an alien whose homeland had been destroyed by Frieza's faction, who had fled to Earth and trained tirelessly in hopes of one day defeating Frieza and avenging his people.
Yinsen did not immediately reveal the background he had fabricated. He still needed to find time to coordinate their story with