In a word, except in minor differences appreciable or at least important only to the special student, the modern Japanese are a homogeneous people.
In origin and formation, this people is a composite of many tribes.
Roughly outlining the ethnology of Japan, we should say that the aborigines were immigrants from the continent with Malay reinforcement in the south, Koreans in the centre, and Ainos in the east and north, with occasional strains of blood at different periods from various parts of the Asian mainland.

In brief, the Japanese are a very mixed race.
Authentic history before the Christian era is unknown.

At some point of time, probably later than A.D.200, a conquering tribe, one of many from the Asian mainland, began to be paramount on the main island.

About the fourth century something like historic events and personages begin to be visible, but no Japanese writings are older than the early part of the eighth century, though almanacs and means of measuring time are found in the sixth century.

Whatever Japan may be in legend and mythology, she is in fact and in history younger than Christianity.