Does the font setting work for any other font with Japanese?
Are you sure the font in questions can display Japanese?
Can you show a short sample code that demostrates the problem?
This works for me:

perl -MEncode -MTk -e 'my $j = decode("utf-8", "\xe6\x97\xa5\xe6\x9c\x
+ac\xe5\x9b\xbd");
    my $w = new MainWindow::;
    $w->Label(-text => $j,
              -font => "-adobe-helvetica-regular-r-normal-*-12-*-*-*-*
+-*-*-*"
             )->pack;
    MainLoop()'
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