yes, of course that would work.
if you want to try, search for
"浜崎あゆみ"
you'll see you get tons of results from amazon.co.jp
and none in mediamonkey
(search with none of the tracks selected, that way you're searching only what you've just typed in, and not linking the search with the track information)

Maybe this is a silly question, but have you tried the same thing directly on the Amazon website, i.e. searching japanese names albums/artists?

it doesn't return any result if you actually enter japanese into the search field and search for it.
so right now I'm having trouble tagging japanese named artists with japanese named albums, since there's no way to find it without entering the actual japanese name.