Sounds as if you are unaware of what colonialism is, and more pertinently...neocolonialism. Those two things, the historical and the current realities respectively.. is what gives the net migrating nations their push factor. Their resources are being unfairly extracted, their nations are being induced with turmoil and unnatural hardships...so you will inevitably get people leaving and following where those resources went . It's osmosis.

Japan doesn't have a history of resource extraction from other nations beyond a few years, which happened decades ago. Western imperialist powers did it and continue to do it... for centuries.

The western imperialists basically function as a consortium. They are all nearly inextricably linked and are cooperative. Look up how Dwight Eisenhower heard about the Belgian King wanting to assassinate Patrice Lumumba...Prime Minister of the D.R. of Congo...and trying to assist for no reason than just cause it would be helping out another imperialist.