I wear Uniqlo (euro or US which I believe is the same sizing). I have some Japanese ones too and they are to regulal underwear what Japanese condoms are too regular condoms, but worse. Not a good feeling... But if you size up on the Japanese Uniqlo, would it not be nearly the same as the US ones? Or are you saying dimensions in some areas are far smaller across all sizes? I noticed the Lad underwear is cut less generously in the front than the CK. I actually like this since it holds one's stuff in better. Makes me wonder if I'd actually prefer the Japanese version over the US one.