That's pretty much the game gives you as to why the Kuei-Jin are scary. Because they're Asian. (I think the blurb may have actually said "oriental" which is a bit gross in and of itself - oriental is the word used for objects, not people, since we're out of the reign of King Edward and all.) And therefore mysterious because nobody knows what they're about because ASIAN OOGABOOGABOO. I can try to dig up the exact loading screen with said blurb on it if you'd like but I'm not entirely sure I got a screenshot of it.
But I have this odd feeling that whatever I do you're going to shoot back with how I'm wrong so ¯\_(ツ
_/¯