Normally, to change the font of Nitoro+ game, change the values of LoadFont and SetFont in function_box.nss and sys_backlog.nss
Probably, just changing system.ini will not change the font.
It was difficult to translate CMVS Engine games as there was no way to repack the files to CPZ. But it was found that the games work without packing to CPZ. You can try the following way.
Example: Mirai Nostalgia - H Scene Trial Edition
Editing scripts:
1. Unpack "data/pack/script.cpz" using arc_conv and move "code" folder into "data" folder
2. Dump "data/code/snzh00.ps2" using Ps2TextDumper.exe and edit snzh00.ps2.txt (Save in UTF-8 without BOM)
3. Repack snzh00.ps2 using PurplePS3Packer.exe
4. Edit cmvs.cfg to change fonts
[MESSAGE_INFO]
FONT=MS Gothic