I think you'd have to find a font that can handle simulaneously the Japanese and French (i.e. accented) characters... Maybe some unicode stuff? I didn't look very hard for such a font, but I don't think that it's easy to find.
Most of the time I tried (on various platforms), the Japanese character encodings conflicted with the accented characters encoding, so in the end I had to chose between Japanese and French, or use multiple fonts - but not many applications can handle simultaneous multiple fonts displayed in the same field, for instance. At least on a PDA.