Are you sure? Japan is maybe 99% homogeneous? I live in central Tokyo and I can go on for days and days without seeing a foreigner!
> it will inevitably introduce social strains
Sadly, yes. I've observed this on few occasions.
Reading comments on this thread below yours, there are a surprisingly high number of people on HN who think all Asians look alike. Spend a few months in an Asian country and white people begin to all look alike while Asians become quite distinct.
Also, it is quite easy to tell most tourists apart from foreign immigrants. The backpacks of gear, maps, constantly getting lost, or participating in things mostly designed for tourism gives it away.
If you're a tourist, you're very likely to carry certain cultural mannerisms or clothing that give you away, but otherwise stripped down naked there's very small physical differences.
If the foreign Chinese or Korean person has assimilated (learned the language), you would hard pressed to tell.
Masayoshi Son, the richest Japanese person, is ethnically Korean, and he had switched his last name back to his Korean surname so that he could be recognized as a Korean.
Much of what you perceive to be differences in phenotype among Asians are usually geographical or culturally acquired differences. For example many people think that Filipinos must have dark skin, or that if you have fair skin you must come from Japan or South Korea, but in reality that has more to do with how much sun those respective cultures manage to avoid, and skin-care products.
Facial blindness for racial features occurs when you're not accustomed to having to noticing such features. Most homogeneous regions can readily identify outsiders: they just look different. They're less likely to be able to identify where the outsider is from.
Guessing from facial features, with great but not perfect accuracy, is a skill. Like any skill it needs to be practiced. It is also never 100% accurate but I'm right most of the time.
Korean people have rounder faces and a less distinct chin than Japanese people. Chinese people are a bit in-between the two in terms of head/face shape. Koreans tend to have smaller noses and less pronounced cheek bones. Japanese have thicker eyebrows. The "double eyelid" is more common and prominent in China/Japan than Korea. China varies a bit more by region - but the people from Guangdong look different from those in Jiangxi or Gansu.
As a rule of thumb the north-south effect applies to Asian just like it applies to most of Europe: people in the northern regions are on average taller with lighter skin than people in the southern regions.
It also isn't just East Asia. Most people have difficulty telling African people apart because it isn't a skill most people need to practice. In East Africa, (eg. Uganda, Kenya, and Somalia) people tend to have larger foreheads (or more accurately: higher hairlines) than in other African countries. I actually learned a lot of this from watching a linguist, who often goes out to speak with people in public [0]. To approach and open a discussion he often has to guess their ethnicity in order to guess which language he should speak. He does so with a very high accuracy, including regional differences for Chinese people (he speaks Mandarin and Cantonese and from what I remember a few more regional dialects). He often does this without ever hearing the other person speak first, although he does sometimes overhear them speaking and butts in to chat.
>If the foreign Chinese or Korean person has assimilated (learned the language), you would hard pressed to tell.
I attend a Japanese class (in the US) with Chinese, Korean, Filipino, and Japanese students many of whom speak the language fluently. I did not have any trouble guessing except for one man who was half Korean-half Japanese. Now this isn't a topic I always bring up and it's not like I go around trying to guess peoples' ethnicity, but among friends who are learning a language together it usually comes up at some point.
Again, to reiterate: It is never 100% accurate. People are of mixed races all over the world, very few people are completely homogeneous. Recessive traits can appear, maybe they were raised in the South but by Northern parents. Maybe they're just a tall shut-in. Maybe they have a lot of makeup on. Maybe their diet was very different growing up. There's a lot more that goes into looks than just genes.
Just because most people can't play a 7-string guitar doesn't make it impossible to play a 7-string guitar.
I live in Kagoshima which has one of the lowest rates of foreigners in the country and nearly every time I go into the city centre I spot a foreigner. My daughter's (standard) daycare has at least 2 other foreign kids. Convenience stores have Chinese students working part time.
99% homogeneous still sounds about right though.
I’m quite surprised to hear this actually. I visited Japan recently and I consistently saw other foreigners around the center of Tokyo.
I think the only time I _didn’t_ see any other foreigners was when I was out in Ōtsu, but that’s sort of out there for most visitors anyway.
EDIT: I should add that I tried to make a point of walking around a bit, so I don’t think I was just taking the subway to commonly visited spots.
Of course, but those were mostly tourists?
(And they don't exactly have a mutual love for each other)
Korea is the country that breaks hand scanners. By that I means the sort of biometric measurement devices used for secure entry to doors. Korean hands are pretty much identical.
You are right though, the occasional Japanese person is going to be very hard to spot since they usually fall within the range of Korean diversity.
https://www.japantimes.co.jp/news/2019/03/22/national/number...
And with a population of 126.8 million people that means that 2% of the population are foreign.
But go to Shimokitezawa or Gakuendaigaku or anywhere off the beaten path and foreigners will be few and far between.