I don't disagree with your technical assessment of gene flows. It is as accurate as history and genetic mapping can provide.Most yellow skin ancestor is from han chinese and of course japan has its own indigenous peo like the jomon but during the yayoyi period, the chinese and korean move from china to japan and mix with the jomon . Korean needless to say but they have some mongol blood and that is why they are taller with smaller eyes. Mongols has ruled china during yuan dynasty so the mongols and han chinese have already intermarried. Vietnam is part of china for around 1200 years so that is why there are some Vietnamese look like chinese.
just pointing out that a majority of those races you mentioned will disagree with you about same race.
meaning... people will always look for a reason to fight with another people over "race". just trying to be of service.