Racism has been raised to an art form in east Asia. They all can’t stand each other. The Japanese are particularly sensitive about their origins. A study came out a few years ago indicating that the majority of modern japanese are genetcally of Korean origin. The Japanese had a fit, and refused to accept the results.
CC
There also was a study that says that samurai origins go back to an Ainu guard force of a very early emperor. That historical study disappeared off the Japanese Archeological/Anthropological radar screen very rapidly!
I believe if memory serves it was an American author.