Are the Japanese from ancient China?

The Japanese are actually adherents of the Qin Dynasty in China.

In order to live forever, Qin Shihuang sent alchemist Xu Fu to Yingzhou in the East China Sea to look for elixir, but soon after going out to sea, the ship was overturned by the waves, so these terrible people drifted along the ocean currents to Japan (then called Yingzhou). Because there was no shipbuilding technology, I settled down there (living on sashimi). Qin Shihuang was angry with the local alchemist because he hadn't seen Xu Fu bring the elixir back for a long time, so he staged a farce of "burning books to bury Confucianism". After the demise of the Qin Dynasty, Han inherited the orthodoxy, and after a period of rest, his national strength recovered, so he remembered these Qin adherents. So Emperor Wu of the Han Dynasty sent generals across the sea to conquer these people, but due to the limitation of navigation technology, the conquest failed.

Therefore, after the founding of the People's Republic of China, in order to overwhelm China everywhere, Japan named its own emperor "Emperor".