Manually Installing PC Mods

Loading modded files without using Reloaded II - Updated 10/24/22
This is an outdated method of installing mods, written before Persona 5 Royal Essentials was released to support P5R PC modding. These instructions are still included for those who rely on the original workflow.
You can also now delete the contents of ALL_USEU.CPK if you are only interested in installing mods and don't need to reference the files. Or, you might also decide to move it to another drive for later use.
Be sure to match the directory structure of the extracted .CPK. For instance, if you're editing a file from the BASE.CPK_unpacked/INIT/ folder, copy the unedited one to your EN.CPK_unpacked/INIT/ folder.
Now you can delete the contents of EN.CPK_unpacked and use it for modded files! Simply drag EN.CPK_unpacked onto CPK.bat to create a new EN.CPK, just like we did with BASE.CPK.
After putting EN.CPK files in BASE.CPK folder, drag the folder onto the CPK.bat to repack it.
  1. 1.
    Copy the files from EN.CPK_unpacked to your BASE.CPK_unpacked folder. When asked, replace the existing files with the same name.
  2. 2.
    Download and extract to the directory containing your unpacked .CPK folders.
  3. 3.
    Drag the BASE.CPK_unpacked folder onto CPK.bat to build a new BASE.CPK containing your EN.CPK files. This may take a very long time, please be patient.
You will need an additional 62 GB of space for the replacement BASE.CPK, since it won't be re-compressed back down to its original size.
Follow the above steps to extract BASE.CPK and EN.CPK. Once extracted, we can move the English files into the unpacked BASE.CPK folder and create a new BASE.CPK. This frees up the EN.CPK to be used for modded files. This one-time operation will save you a lot of time when it comes to repacking EN.CPK later, since the additional 700 MB of files aren't included each time (since you moved them to BASE.CPK).
The game considers the root of each .CPK to be the same folder. EN.CPK has higher load priority, since it's meant to override anything that needs to be localized in English.
Replacement files/folders can be uppercase or lowercase, it doesn't matter since the game loads them either way! Just make sure the .CPK filename is all uppercase.