Since I have distant ancestors that were "black" and "asian" I feel like I should be able to answer this question.
While living in Korea, I always found it totally bizarre and awkward how every last foreigner I'd see out on the street would seem to feel obligated to acknowledge me in some way, even if (and this was usually the case) I did not know them from Adam. I'd always get at least a smile, a head nod, or sometimes a "hey, how's it going?"... as if just because of the fact that we were both not born there we must have something substantive in common. Or as if we had some secret conspiracy or were members of a special club. It baffled me and always made me laugh afterward, especially the random head nods I'd get walking along the street.
The only place I wouldn't get this would be the neighborhoods where foreigners were commonplace (Yongsan, Hongdae, Gangnam, Insa-dong) or the majority (Itaewon). But everywhere else I'd get the "hey hey! we're both White! represent!!" thing. It would make me laugh.