Came across an interesting (but somewhat peculiar) website called "Mythusmage Opines" with articles discussing "the races of AErth." At the bottom of the article called "Minor races" there is this passage about the Ainu:
"Far to the east, north of the Mixed Eastern Azirian Yellow Japanese, live the Ainu. The Ainu are the last remnants of the Jomon people, driven north by the ancestors of the Japanese when they invaded from southern Korea. Once considered White, the Ainu are now known to belong to their own race. Having just a few thousand members, the Ainu are the smallest of Ærth’s races."