The main font - miniwakuwaku only supports Latin and Japanese (and also some weird shapes and Japanese brackets). For symbols not present in the main font the game uses the Noto font family in a bold weight.
Also the files for miniwakuwaku are kinda weird and for a lot of symbols which it doesnt have it instead draws a zero width character instead of saying that it doesnt know how it should look like which would allow the tools you use to use a different font. I think max made a script that fixed that issue of miniwakuwaku for use in textreme. I will let you know if i find it.