Reminds me of an old joke.
Question
How can you tell the difference between a Russian and a Finn?
Answer is
You can't, but a Finn can tell the difference at two hundred yards over open sights in a driving blizzard.
There are several ethnic groups among the Japanese. The "Yamato" were the ruling military class and in those days their appearance was markedly different from the average Japanese from more common stock.
These days theres been enough interbreeding with other races, and acceptance of Korean and Chinese fathered by Japanese troops that Japan is on its way to being an Asian melting pot.
During WW2 the Japanese made use of conscripts and volunteers from occupied countries. It was not uncommon for the majority of Imperial troops in some regions to be Korean , the only Japanese present being the officers.
Chinese volunteers serving the Japanese even had their own specialized rifles, a copy of the obsolete Japanese type 30 rifle chambered for the 7.92 Mauser cartridge which was the standard cartridge of the Chinese army at the time. The rifles and ammunition were manufactured in a captured Chinese arsenal.