non-US-ASCII file names (e.g. Hiragana) on Windows

I've created a file with unicode characters in its name (using Java):

 new File(dir, "\u3041\u3042\u3043\u3044").createNewFile();

The file name is stored correctly on disk, because if invoking a

 dir.list()

the name is listed correctly.

When opening this directory in the Windows Explorer (German Windows XP SP3), it shows 4 boxes - which most likely is a problem of the font not supporting these characters.

When launching 'git status' from the git shell (msys 1.6.5.1.1367.gcd48 from 7zip-bundle) it only shows me 4 question marks. I would have expected to see the non-displayable characters escaped like it did with the umlauts on OS X.

Even adding fails:

$ git add . fatal: unable to stat '????': No such file or directory

What should I do to make Git recognize these characters?