The Jomon, Chinese, white people, Sa'ami and a few others all have a common ancestry that spent much of the last Ice Age in South Central Asia.
There were a couple of good interstadials and that common ancestry moved North and then split into two groups, one going West to Europe and the other going East north of the Himalayas to the Far East.
That was about 35,000 years ago ~ when those cave paintings show up.
Once the East Asian branch moved East of the Himalayas and out of the desert country (still present just NW of Peiping) they split into two groups. One group moved on East to settle in the plain between the Huang Ho and the Yangtse. The other group moved to the South East. Over vast amounts of time many of them settled in what is now Japan but then was just an extension of the Asian Mainland into the Pacific.
Eventually those two groups were divided as the ocean rose at the end of the iceage 14,000 years ago. The folks in Japan are who we call the Jomon, and later the Emeshi (who turned into the Samurai under the leadership of an invading Chinese leadership group we today call the Japanese Royal Families and the Daimyo Families).
In one of those quirks of fate the Jomon's relatives had moved to the East Asian Maritimes. When the Medieval Japanese evacuated Hokkaido and the Northern Islands the Jomon-type people in the Maritimes simply moved into the coastal areas of the North and became known as the Ainu. Some Ainu also settled in Taiwan before the Chinese. Apparently more modern Japanese pirates settled there too!
The greater part of the East Asian people settled China so you'll want to see their history. The furthest West Chinese ran a trade route from Siberia to India. They produced Buddha (among others) and ruled much of India for a number of centuries. They acquired all the good lookin' gals in India and consequently ended up looking a tad different than all the other East Asians.
About the time of the start of the Dark Ages they invaded Japan, took over the Chinese rice growing regions (which had been under development for over 1000 years) and began a multicentury war against the Emeshi (the Jomon).
The Cro-Magnons that went West in that interstadial appear to have occupied all of Europe. Most of them were wiped out by the advancing ice and deteriorating climate. Some small populations remained in three Refugia ~ one of which was at the Western end of the Pyranees, on in Sebia and another further South in Italy. There are probably more but we just haven't discovered them yet.
As the ice began melting 14,000 years ago part of the people in the Western Refugia went due North. Part of went East and North East. Part went South to North Africa. Some part of it certainly went far East!
While "trapped" in the refugia all of these populations developed some different characteristics. The Sa'ami, being the ones longest isolated from the others, and having what seems to have been the smallest population, retain many of the ORIGINAL characteristics ~ rounder heads, different eyelids, coloration, and so on. The group with the largest population, those left in what is now Spain and France, diverged the most from the original base (larger populations allow new alleles to propagate more widely). That's where you find the recreation of the Northwestern European Red Hair ~ and possibly even the gene for suppression of pigment production. Blondism arises out of yet other genes and, in most European populations may be of quite recent origin ~ maybe within the last 5000 years ('before which they were all swarthy hairy people looking remarkably like their cousins in India and such).
In the far North where the Sa'ami live blondism arises out of simple selection for a low level of melanin production ~ since you gotta' have all the light skin you can get to produce enough Vitamin D to live there. Other "white" populations, including the Chinese, have genes that actually block melanin production except under certain circumstances ~ like "it's summer and time to tan".