How to convert Japanese OTF fonts to use with FOP

Question

I need to generate a Japanese language PDF document formatted with a Japanese font, using Formatting Objects Processor (FOP). I have a few potential OTF fonts that I would like to use. Unfortunately, FOP does not support OpenType (OTF) fonts with CFF glyph data. I would like to convert the OTF fonts to a FOP-compatible format.

I have installed FontForge, and I am trying to use it to convert the fonts to TrueType (TTF), but each time, it generates incorrect font files -- or at least the Japanese characters are not converted.

How can have FOP to read my font? In what format do I have to convert them, and maintain the multibyte capabilities?

Note: my English-language setup is working correctly