ttf-pc9800 is a font converter for the NEC PC-9800 series. It converts the FONT.ROM of the PC-9800 into TTF format. In order to use it, you need the FONT.ROM of the PC-9800.
Place the font ROM image in the data/FONT.ROM and execute the make command.
Upon successful execution of make, a TTF file will be generated in the dist directory.
$ sudo apt install git make ruby fontforge-nox potrace bdfresize
$ git clone https://github.com/hikaen2/ttf-pc9800.git
$ cd ttf-pc9800
$ cp </path/to>/FONT.ROM data/FONT.ROM
$ make
Note: FontForge may give the following warning, but there is no problem: "I'm sorry this file is too complex for me to understand (or is erroneous)."