Japan used to be a white country like 15-20 thousand years ago when the continent Lemuria was still above the water. Before the Younger Drias Impact [I know I spelled this wrong.] cataclysm where enormous amounts of astroids, ice, and planetary debris fell to Earth. This impact had so much pressure that it sunk the Lemurian continent under the Pacific ocean and raised up the Himalayan and Andes mountain ranges, which were on the edges of the tectonic plates that were pushed down.
But before this, the White Lemurian people, which this is where White people originally came from on Earth, had visited and lived on Japan. Asian and White people mixed together here at this time, so the Japanese have had some White DNA ever since then. And with all the wars between Japan and Korea where both sides have raped each other's people many times, the Japanese and Koreans have very similar DNA to each other so the Koreans also have some White DNA. This race mixing happened so many thousands of years ago between White and Asian that the DNA is not the same as a White person because everything has alloyed together, but you can still see some White phenotype features in things like the pale skin and increased height compared to some other Asians.