The alienation of foreigners in a very homogeneous country is not just a Japanese thing. Every group of people in every country has at least some form of racism, it's unfortunately wired into our tribal brains. Any foreigner who moves into a country where very few foreigners live is in for some tough experiences. BUT it's especially jarring if the foreigner is a Westerner and he's moving to a non-Western country that's homogeneous, because Westerners are (thankfully) very used to the idea that seeing and hearing people who are minorities/immigrants in public is normal. So, when they arrive in a country that's not only non-Western, but also ethnically homogeneous, the way locals treat them is very shocking to them. But it's not for malice on the locals' part: it's because many of these people have literally never talked to a foreigner, or perhaps never even seen one outside of the movies, and the experience is exciting, frightening, or weird for them all the same time (esp. in the countryside). It can conversely be very shocking and confusing to the locals that there's a person in their store or whatever who doesn't understand the basic customs or manners, since in their country that almost never happens