The initial wave brought the Jomon culture and the second wave brought the Yayoi culture into Japan. Genentic results show that the modern Japanese owe lineages to both Yayoi and Jomon. Now, going closer to the question were Japanese peoples ancestors Mongolian? read more
Many Koreans and Japanese resemble the Yayoi. The Yayoi people came most likely from some parts of the Korean peninsula and many Koreans look quite like Mongolians. So it may seem that in the end, the ultimate ancestry is Mongolia. read more
In fact, the Philippines and Indonesia were also connected to the Asian mainland. This allowed migrations from China and Austronesia towards Japan, about 35,000 years ago. These were the ancestors of the modern Ryukyuans (Okinawans), and the first inhabitants of all Japan. read more