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If it's a large, complex site, it's probably best to do whatever helps you to maintain it most efficiently.
.../fashion/japanese/
I agree, that should be quite enough. Also, it makes sense, if you think about it, to organize your directories so the most general terms are closer to the root.
the only reason i'd want it would be to rank for the keyword "unique japanese fashion".
If you're thinking about Google, I'd be careful about getting too right on these days. G is getting very sensitive about over-optimization. That said, I don't think the path names have that big an effect on rankings. The highlighted terms do attract the eye in serps, though.
Also, if you're ranking for [japanese fashion], ranking for [unique japanese fashion] should not be so difficult that it makes sense to build a directory for the word.