[Help] Editing .DAT font files

[6Kyojin4]

Hello I'm looking to start up a Japanese Machine Translation Project for the DS RPG "Black Sigil: Blade of the Exiled". As a apart of the project I need to edit the FontData.dat which I think holding the character themselves and FontIndex.dat holding addresses of each letter in the font. I need help finding a way to edit both and add additional characters, advice much appreciated
https://www.romhacking.net/forum/index.php?topic=39306.0