Ok, in Cambridge dictionary
Japanese (n): a person from Japan. Ex: She married a Japanese.
The Japanese [plural] (n): the people of Japan. Ex: The Japanese make excellent cars.
Japanese (a): belonging to or relating to Japan, its people, or its language. Ex: the Japanese stock market
So, "Many Japaneses" or "Many Japanese people"? Which one is more common?
I feel that "Many Japaneses" is a bit strange