If you are looking to modify student stats like height or BWH, you can use the Character Editor by Kirara Kurashiki.
extracting specific assets from this zip, or Gal*Gun Double Peace - Modding Guide - Steam Community File: Gal.Gun.Double.Peace.zip ...
Always remember to back up your original .upk or .ini files before overwriting them. Launch Game: Start the game and enjoy the new additions! Common Tools for this Game: If you are looking to modify student stats