User blog comment:ヌヌハラ/alice-tools v0.1.0/@comment-45345722-20200330215646/@comment-44256294-20200331001630

I believe adding new fonts would require editing the game's .fnl file. Unfortunately I don't know how the data in these files is structured. I tried looking for signs that it contains .ttf/.otf files but came up empty.

And I'm just guessing the .fnl files contain fonts based on filenames. It might contain some other typesetting-related data and not the actual fonts themselves. Older system 4 games are hardcoded to use MS Micho/Gothic fonts, so changing the font there would require editing the executable.

So while I would like to write a tool for changing fonts, I am currently unable to do so due to lack of knowledge about the relevant file format.