Why do Japanese and Korean people immigrate to other countries if their countries are already so wealthy?

I've seen Japanese and Korean communities in every western country that I've been to. My question is, why do they move to these countries if their home countries are already so wealthy and developed? Japan's passport is literally the strongest in the world, with South Korea in second place. I get why Chinese people and Vietnamese people would immigrate -- - both countries repress their citizens' rights. But why do the Japanese and Koreans immigrate?

Why do Japanese and Korean people immigrate to other countries if their countries are already so wealthy?
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