Firstly, I appreciate Golden Yoshi for providing people with a better explanation of how-to for this tool in his post and answering people's questions in place of me. And, since he decided to release it, I also give him another thank-you for beta testing and reporting errors before it even got usable at all.
Secondly, thanks you all who gave it a try for that and giving me some feedbacks.
Like he mentioned, I still intend to update the sprite some time, but I don't know when.
But for now, I release a small tool
which I dug up from an old folder that will allows you to edit the font comes with the tool easily with YY-CHR.
First, you run the tool in this usage;
vwffont_convertor.exe -d vwf.bin output.bin
vwf.bin is the font file comes with the archive. After output.bin is created, open it with YY-CHR and set the graphic format to 1bpp. Now, letters are rendered in 16x16 blocks, and you can easily edit the font with YY-CHR now.
NOTE: Although each block is 16x16, the actual available range is 16(horizontal) x 12(vertical). Please remember it.
After you're done, you need to encode the file; run the tool in this usage;
vwffont_convertor.exe -e output.bin edited.bin
Now, the edited.bin (for example) and a new width.bin are created. If it's alright to overwrite the existing vwf.bin, rename the edited.bin to vwf.bin, and reinsert the sprite to actually apply the graphical change. If you even don't care the vwf.bin is always overwritten, you can just directly specify the output path to vwf.bin instead of edited.bin.
Well, since this program is old and I think I haven't tested that much, so please tell me any issue if you found. (I recommend backing the files up first anyway.)