https://github.com/FanTranslatorsInternational/Kuriimu2
use this.
What are you trying to mod, exactly? if you're trying to actually change the game's mechanics, you're gonna have a hard time, there is 0 documentation on it. If you're trying to extract textures or sprites, you'll be looking for .xi files. If you're looking for models, you're out of luck for the time being.
The concept is a Dungeons n' Dragons game come to life, and the party are 80s teens. They have different skills, one even has magic powers, and they fight small monsters and boss monsters