i think there are crushes here LOL
From what i know, most koreans are probably a mixture of Coastal South-Eastern Chinese (around present day Zhejiang and Shanghai) and Altaic groups from somewhere around North Korea/Manchuria. The reason is because of the korean method of cultivating rice, originates from Southern China. This same group of people, some of them later went to Japan and brought tattoo culture - same method both used by the Yue of Zhejiang and the Japanese people.
Japanese people are for sure a mixture of South-Eastern Chinese, Korean, the aboriginals and the polynesians. The following groups were influencial to current Japanese culture: Chinese -> agriculture, loan words and religion, Koreans -> grammar, Aboriginals and polynesians -> culture [not too sure about this one].
You seem to assume that technological transfer (rice cultivation) must involve migration and intermixture. Why is that?
Are Russians Orthodox Christians because they are half Greek or significantly Greek in ancestry? NO. The vast majority if Russians have no ancestry from greece and no Slavic ancestry that lived under Greek/Byzantine Rule.
Are the majority of Indonesians or even 1/3 Arab or Persian in ancestry because they are Muslim?
I use Japanese, Korean, and German technology all the time...does that say anything about my ancestry.
Reality is regional and even global trade networks go back thousands of years.
When silver was found in North America and South America by the Spanish and Portuguese it seriously hurt the silver market in India and China...this was in the early 1500s...when the vast majority of Chinese never saw a white man or even heard of the "Americas" they were using "American" silver.
Egyptians widely traded with Greeks, Persians, and various peoples in the Middle East and contributed little or no ancestry to those people, although we can find Egyptian things among their ancient archeological sites and vice versa.
Language is the best example...most people in the world never invented a written language. No one in Europe invented a written languange from scratch...does that mean all Europeans have Phonecian ancestry? Are all SouthEast Asians Indians or mostly Indian?
If most people around me are farmers to some extent and I traded with a people who traded with someone else who found or heard of a new way of farming and I saw the benefit I don't have to marry their daughter or have their sons take over my village for me to seek to emulate it. This is human nature to mimic successful behavior.
There is very little evidence that Japanese people have any Yue evidence and most of it that has been presented on this site is circumstantial as I showed in a post in this section...it is very poorly written evidence. Yue does also not equal Han.
Modern Chinese in those areas, like Fujian are a mixture of Han men and Yue women.
It is like saying Southern French share ancestry with Basque so they are the same people as people in Mexico. Uhm...well there are many people who are of Northern Spaniard ancestry and actually Basque ancestry in Mexico but most of those people also have strong Amerindian ancestry.
What is best is to say that they share some common ancestors.
Yue people (if some moved to Japan) does not make the Japanese "Han" or the Yayoi Han because people from that area over 2,000 years later are Han today.