Xu Shi had made himself king in Japan and had no desire to return to Qin. But he was still a man of Qin, and he was terribly afraid of Qin Shi Huang! He thought that if Qin Shi Huang learned of this someday, or if Qin Shi Huang achieved immortality and happened to come to Japan somehow, he would definitely die a miserable death!
So, after ruling as king for several decades, he passed the position of Emperor on to his descendants!
However, when he first arrived in Japan, it had still been a barbaric land, primitive to the extreme, with slash-and-burn farming! Thus, to better rule those primitive inhabitants, better conceal himself, and ensure that his descendants could continue their lineage!
Qin Shi Huang had dreamed of a dynasty lasting for ten thousand generations. Though Xu Shi was not particularly capable, he too hoped that his rule over a nation could be passed down forever!
Moreover, he had originally been an Alchemist, part of the precursor to Taoism, essentially a rather primitive kind of Taoist priest. So he put his mind to work, combined Japan's rumored myths and legends, concocted a bizarre mishmash of mythological tales, and founded Shintoism in Japan!
Xu Shi not only assigned Japan's Amaterasu to be his own mother, but also gave her another title: the Sun Goddess!
As for Japan's Emperor—namely, himself—he was made into a descendant of the gods! And because it had to fit Japan's ancient legends, his mother, Amaterasu, was directly born from an eye!
There was no helping it. According to Japan's legends, the three gods—Amaterasu, Tsukuyomi, and Susanoo—were born respectively from the left eye, the right eye, and Susanoo from a nostril!
It simply made no sense! Every god in Japan's mythology had been born while Izanagi was