>Japan is intensely racist

Would you care to provide some substance to this claim? You're tarring over a hundred million people with a very nasty brush.

Japan is intensely racist. My spouse lived there for a year. When she went about her business outside, small children who saw her would literally burst into tears screaming to their parents about gaijin.

That never happened to me, and I have been living there for 8 years now.

But I would agree that Japan is generally racist, as in most Japanese believe there are fundamental differences between people due to what they call race. I am not sure whether most Japanese would consider Korean a different race, but I would not be surprised either.

See below, written 10 hours before your question. There is still overt, broadly-recognized and tolerated ethnic and hereditary discrimination in Japan, not just in hiring and school admissions but in stuff as basic as housing. Japan appears to be stuck in the 1960s in terms of public policy on this issue.

Below is a discussion of Burakumin and ethnic Koreans in Japan, which doesn't appear to be racially predicated, unless you're operating under an unusual definition of race. You've specifically claimed that "Japan" is "intensely racist". Are you going to claim that Koreans and/or Burakumin are racially distinct from Japanese?

Whatever semantic thread you're trying to cling to in order to keep this argument alive, I'm not interested.

No, please, it's not semantics, I'm directly refuting your claim. If burakumin and ethnic Koreans in Japan aren't racially distrinct from Japanese people, then discriminatory treatment of those people isn't racism. Your example doesn't support your claim. I'm inviting you to please explain how the example supports your claim. Maybe a good start would be providing an operational definition of "racist", as in "Japan is intensely racist".

Their point was that Japan is ethnically and culturally homogeneous enough that they don't feel the need to implement exclusionary zoning, regardless of how racist and xenophobic the general population is.

Japan is neither ethnically nor culturally homogenous despite an image at home or abroad regarding this; see Sugimoto’s Japanese Society if you want a book-length takedown of it.

For an example of how this affects who can live where and how where one lives affects non-residential opportunities, you can read up on burakumin (a disfavored heredity pseudo caste). Burakumin status still exposes one to highly non-trivial societal discrimination, and is primarily observable based on “Have you or yours ever lived in a burakumin neighborhood?” This makes e.g. historical maps which mark out burakumin neighborhoods into socially contentious informational hazards; Google Maps had to take them down after a (utterly well founded) fear that at least some employers and schools would cross-reference neighborhoods with current or historical applicant residential addresses and then go full Harvard University on them.

Similar observations can be made about ethnic Koreans, Japan’s rapidly growing population of long-term resident foreigners, etc.

Key word is "ethnically and culturally homogeneous enough". And since we're talking about political policy here, domestic image is what matters here.

The actual numbers are not known because they aren't collected as part of the census, but the government estimates that upwards of 98% of the population is "ethnically" Japanese. Furthermore, many of the ethnic Koreans that you mention, as well as ethnic Chinese (the next biggest group, as I'm sure you already know), are culturally fairly assimilated, even if many are second class (non)citizens in the eyes of laws and much of society.

My understanding is that this is not in fact true: there are significant populations of disfavored minorities in urban Japan.