Yes, its almost impossible to complete tell the difference between groups of North East Asians. There are unique facial characteristics amongst Chinese, Japanese and Korean that can be used to tell them apart, but sometimes this doesn't work. There are also blurring of features. For me, as a Northern Japanese who has Ainu blood (my mother is half Ainu), I have facial characteristic that is unique from typical Japanese. I don't have sharp eyes as most Japanese, rather, my eyes are quite almond shaped, lacking the epicanthal folds that defines most East Asian obicular occuli. I have more body hair and i can grow my facial hair quite fast; and I'm taller than some of my colleagues (I stand at 6foot 1inch, or 185 cm). I get this from the Ainu blood i suppose. This is a trait most Northern Japanese have; we are lighter skinned, harrier, taller, larger build, oval eyes; very unique from the Japanese beauty of say Honshu, Kyushu and Shikoku. As for telling some Japanese from Chinese; i can. But i have difficulty telling apart Korean and Japanese.