Thank you for your time and help!Ok, this one was annoying as fuck. Not because it was hard, but because it show me a bug in my sigCorrector tool (I'll update the thread once I validate this).
Download the attached archive, there's many files inside, one in a "renpy" folder.
Extract it on the main game directory (where you usually put unren.bat), and confirm that you don't care that the "renpy" folder already exist.
Then do like you do for unren.bat to launch unrpa.bat, it will extract the content of the "archive.rpa" file.
Once it's done, do the same with sigCorrector.bat to revert the change they made to the rpyc files.
Then now you can play the game, look at the CG, and ask unren.bat to unrpyc the files.
You rock!