Not much has really changed in Japan since the fuedal period, in fact, a lot of the policies from the feudal period play a direct role in modern day japan. Anyways Immigration is always an issue with many aspects of Japanese life, without a stable population growth in Japan the japanese people could easily disappear in a similar way that many ethnic groups in America have disappeared over generations or in east europe where several ethnic groups banded together to form larger nationalistic identities such as the creation of the russian "ethnic" group. Japan has suffered a similar fate with the designation of a Yamato people that does not have a true ancestry. Ethnic groups in Japan are unacknowledged as the Ainu people suffer from discrimination on a systemic level in the Hokkaido region. Comments like this show true ignorance on topics in relation to societies. By your logic should we all just die out and let the Indian and Chinese ethnic groups become the dominant and only groups in the world? Is everyone actually just Han Chinese?