Important

The "new" encryption scheme that works on the newer Light.vn version is stripping the original file name, so I can't recover it.

We're missing the original file extension, but we can guess it by reading the file header and set the extension based on that,

For the time being you need to do it yourself by grabbing a hex editor program like ImHex, find the magic header, do some Googling then rename the file.

Download Light.vnTools at Releases.
Unpack/Decrypt:
Drag and drop .vndat / .mcdat file(s) to the LightvnTools.exe.
Repack/Encrypt:
Drag and drop unpacked folder/file(s) to the LightvnTools.exe.

Credits

Thanks to takase1121 by providing proof of concept at: https://github.com/morkt/GARbro/issues/440

License

This project is licensed under GNU GPL 3.0.

For more information about the GNU General Public License version 3.0 (GNU GPL 3.0), please refer to the official GNU website: https://www.gnu.org/licenses/gpl-3.0.html

Disclaimer

This tool is intentionally created as a modding tool to translate the visual novel game created with Light.vn game engine. I didn't condone any piracy in any forms such as taking the game visual and sell it illegally which harm the developer. Use the tool at your own risk (DWYOR - Do What You Own Risk).