I think most schools in Japan and Korea and other places don't hire other nationals due to visa restrictions, since only a few nationals can get the work visa in these countries, but you'll also find other schools in Japan and Korea etc that reject other native speakers for various unknown reasons. I've met some black South Africans that couldnt get jobs in Korea.

Even though the Chinese government issues visa to various nationals, some schools still reject other qualified English teachers for unknown reasons, maybe racist reasons or due to accents. The first question most schools ask if you call for a job is " where are u from? " a few will ask "are u black or white? " or "send your photo". They'll sometimes disqualify you just for these reasons regardless of your experiences or qualifications.

I think the best approach is not to be bothered about discriminatory schools, if you apply and they turn u down for no good reasons, just forget about them and move on, If you're qualified with some experience, there'll always be some other schools that will hire for what u know or can do, not just where you're from or how you look.

They claim that only native speakers can teach English, but since teaching is a skill that is learned, (no one is born a teacher) so its just silly to say only a few people can teach English. Some of those people do not or fail to acknowledge that therere even other English speaking countries. Of most TESL methodology books that I know, Ive not found in any that states only native speakers should teach English. Almost all these books stress that trained and qualified teachers should teach English whether they're native or non-native speakers

The funny thing is, there are even some qualified non-native speakers that are teaching English in English -speaking countries like the US, Canada, Australia and so on, so its just nave if some countries insist on native speakers only.