Do Japanese have Han descent?

Yes, but not as much as we usually think.

The first thing to look at is the blood composition of the Han nationality. Yangshao culture in the middle reaches of the Yellow River in the pottery age is the source of the Chinese nation, and many pottery patterns and production tools are mutually confirmed with Oracle Bone Inscriptions. DNA verification shows that the Y chromosome (that is, paternal genetic marker, which can only be inherited by father and son) has a very high proportion of O3, and the noble tombs are almost 100%, and some tribes, such as Majiayao culture, are O3. The modern Han nationality was formed in the Qin and Han dynasties, and it was formed by the fusion of the Chinese nationality and other nationalities. Today, there are about 70% to 80% O3 in the northern Han nationality in China, and 50% to 70% O3 in the southern Han nationality. The lineage of the Han nationality was basically stable in the Han Dynasty. In the later period, despite the long-term coexistence of ethnic groups, very few Han people accepted foreign descent. The marker paternal chromosomes of Tunguska nationality (Northeast nationality), Mongolian nationality and Turkic nationality are O2b, C3c, R 1a 1 respectively, and the probability of occurrence in Han nationality is 0.

There are about 30% D (Asian short black people, lower castes in Hokkaido and India, the main lineage of Tijen), 20% C (Asia-Pacific brown people, the main lineage of Mongols and Tunguska people except modern Manchu), 30% O2b (arriving in Japan from the northeast of China via the Korean Peninsula) and about 20% O3 in Japan.

This part of Japanese O3 may have arrived in Japan through many ways, which may be brought by Koreans (40%), Liao people and Jin people (it should belong to Tunguska people, and the proportion of O3 was unknown at that time), or it may be brought directly by Han people. Judging from the development of Sanmiao nationality (70%) and Mongolian nationality (ranging from 30% to 0%), it is unlikely that they will bring to the Japanese. The O3 of Koreans, Tunguses and Mongols basically came directly or indirectly from Han or Huaxia.

If all these 20% O3 are counted as Han nationality, then the Han descent in Japan is less than 30%.