I've released an Alpha-Version of my project "Java-RPG-Maker-MV-Decrypter", which works with whole directories and save/renames files by itself...
It has a GUI, try it out! If you just want to decrypt single files, I recommend this version here. (Since you don't need to download it). For whole directories, you should try the Java version of the decrypter! =)
Welcome to the RPG-Maker MV & MZ-File Decrypter. You can easily decrypt files from any RPG-MV/RPG-MZ Project, which are encrypted with the built-in encryption. You can also encrypt them back (Mainly used for translation purposes).
Make sure that you don't use this tool to steal assets. If you want to take a look at the images (which is okay for private use by most laws), feel free to do so, but don't steal them please.
Please select what you want to do:
(No Key) Restore images from a game En-/Decrypt Files to/from a gamePNG-Files (Images - ".rpgmvp & .png_-Files") don't need the decryption code, except you want to re-encrypt them. Please go here for restoring images without a key.
In this area you can De- and (Re-)Encrypt Files from RPG-Maker MV & MZ Games.
You can get the decrypt code from the file:
Click "Detect" after you selected the System(.json) file. If you know the key, you can also just enter it in the text box.
In this area, you can restore PNG files (images - ".rpgmvp & .png_-Files") from RPG Maker games without the decryption key.
First: Please note, that this script is only tested and developed on Firefox. You can help me to make it run on all browsers, by reporting bugs!