Does anyone know what needs to be done in order to write Japanese
characters in FXRuby (the GUI toolkit)?

I'm trying to write them in an FXLabel, but they come out
unintelligibly (they got interpreted as ASCII):

kanji = FXLabel.new(matrix, data[0][0])
kanji.setFont(FXFont.new(app, "MS Mincho", 24))

data[0][0] is a Shift_JIS string read from a file. $KCODE is set to
'S'.