really interesting question. The problem obviously being that you cant put ASCII URLs into an HTTP request. However, you can use the decoded version
if you search for: サッカー (japanese for soccer) you can see the wikipedia page uses the special characters. If you click the result, the actual url used is: %E3%82%B5%E3%83%83%E3%82%AB%E3%83%BC
Google encodes this and displays the characters in the search result - so you benefit from the increased clickthrough as well as the increased relevance.
So, use the decoded version in the filename and Google will wok it out.
Posted: 17-12-2008