> Besides, Japan is a good real world example that you do not need to lean on immigrant labor to stop your country from becoming "dirty"

This was true before about 10 years ago. In last 10 years, there has been a dramatic rise (I mean millions of "technical interns") in low-skill foreigners living and working in Japan. (To be clear: I harbor no resent towards these people.) They work in any industry that needs cheap low-skill workers: agriculture, hotels, restaurants, supermarkets, convenience stores, manufacturing, construction, civil/civic maintenance etc. That said, the friction has been pretty low. The difference between the original late 1990s wave of highly-skilled foreigners (mostly bankers and lawyers) and the most recent wave for low-skill foreigners: The most recent wave arrives to Japan with some Japanese language. (They study in their home country and need to pass a test to demonstrate basic Japanese language skills.) In my experience, their "median" Japanese is much better than most highly-skilled migrants, which helps to reduce the integration friction. Also, the low-skilled migrants have a maximum number of years they can work in Japan. They either need to skill-up and get a better visa (I guess about 5-10% can do it), or they need to return home after their "technical internship" is complete.