it's completely hogwash ...
I am someone more incline to believe Yamato Dynasty ( 大和朝廷 ) was a pure indigenous development of native Wa-jins ( 倭人: Japanese )
not foreign origin.Back then in need of sophisticated Chinese culture,the Yamato Court had welcoming red carpet to Torai-jins as advisors with some awarded nobility titles and such.
Chinese Wei-Zhi ( 魏志倭人伝 ) recorded " direct " contacts between Chinese dynasties & Wa Japan earlier on & uninterupted military,cultural,diplomatic contacts with ancient kingdoms of the other place.No mentioning of language & cultural & ethnicity of collective Wa-jins 倭人 related to natives there.I don't think they were the same people,otherwise Japanese & their language would be intelligible ( don't you think ?? ).
The Chinese helped male the Japanese royalty as we know it today largely in the sense of its cultural influence;
"The emperor was thought to possess magical powers and to converse with the gods. It was therefore considered beneath him to become involved in the day-to-day running of the country. This was left to ministers and advisors. An exception was the period between the 7th and 8th centuries during which several emperors tried to bring the regional clans under central Imperial control. The first emperor to establish such direct imperial rule,
modelled after the Chinese Tang dynasty, was Emperor Tenji who ruled between 661 and 672. Later during the
Nara Period (710~794)
Prince Shotoku, son of the Empress Suiko, created Japan's first constitution and established Buddhism as the country's dominant religion."
"At the beginning of the
Heian Period (794~1185), Emperor Kammu established a new capital in
Kyoto,
a city designed based on the Chinese capital."
The Japanese royal family is the oldest in the world.
www.japan-zone.com
"Around 400-300 BCE, the Yayoi people began to enter the Japanese islands, intermingling with the Jōmon. Most modern scholars argue that the Yayoi emigrated from the southern Korean Peninsula to northern
Kyūshū,
though it has also been proposed that they came from southeastern China. [17] The Yayoi brought wet-rice farming and advanced bronze and iron technology to Japan. Although the islands were already abundant with resources for hunting and dry-rice farming, Yayoi farmers created more productive wet-rice paddy field systems. This allowed the communities to support larger populations and spread over time, in turn becoming the basis for more advanced institutions and heralding the new civilisation of the succeeding
Kofun Period."
"Han Chinese and Southeast Asian ethnic groups were originally thought to be the origin of the modern Japanese ethnic group. Recently, however, both Japanese and non-Japanese academics have predominantly argued that the Japanese are descended from both the Yayoi, who emigrated from the Korean Peninsula, and the long-established native Jōmon people, with whom the Yayoi intermarried. A clear consensus has not been reached."
"The Japanese language has a tripartite writing system based upon Chinese characters."
"The arrival of Buddhism in Japan is ultimately a consequence of the first contacts between China and Central Asia, which occurred with the opening of the Silk Road in the 2nd BCE, following the travels of Zhang Qian between 138 and 126 BCE, which culminated with the official introduction of Buddhism in China in 67 CE. Historians generally agree that by the middle of the 1st century, the religion had penetrated to areas north of the Huai River. Buddhism then made its way to Korea from China, and finally to Japan around the 5th century CE."
"Beginning in the
Nara period, painting, calligraphy, and sculpture flourished under strong Confucian and Buddhist influences from Korea and China. Among the architectural achievements of this period are the Hōryū-ji and the Yakushi-ji, two Buddhist temples in Nara Prefecture. After the cessation of official relations with the Tang dynasty in the ninth century, Japanese art and architecture gradually became less influenced by China."
Japanese people - Wikipedia
From what i have read, the Yayoi people came from both southern China and Korea- also from what i have read, modern Japanese as we know them today are largely descended from the Yayoi people who immigrated to Japan in ancient times- although the Jomon people obviously make up an important part of modern Japanese heritage, they were most thought to resemble the Ainu and the Ainu were certainly always pushed to the side by non-Ainu Japanese in history.
With the Chinese royalty helping found Japan's royalty thing, it's certainly not complete hogwash as the Japanese copied and were influenced a lot in Chinese royal society, like in the 7th and 8th centuries, during which several emperors tried to bring the regional clans under central Imperial control, which was a system modelled after the Chinese Tang Dynasty.
Japanese Calligraphy, painting, sculpture, religion, technology, and society, as well as the layout of important places in Japan, such as Kyoto, have been influenced by China throughout its long history, and people have also immigrated from regions around and within China since prehistoric times. To say that China has had no influence on Japanese royalty and its society is incorrect.
If you believe that modern Japanese today are largely descended from the Yayoi rather than the original Jomon people, then you must also accept that the Yayoi were largely made up of Koreans and Chinese people/people from East Asia (
East Asia - Wikipedia ) then you must accept that the large majority of Japanese originally came from Korea
and China.