1- Install .NET 6.0:
Download it here and Install.
2- Install BepInEx:
2.1) Donwload the version: BepInEx Unity (IL2CPP) for Windows (x64) games
2.2) Download latest version at official's website:

OR
Direct Link to #665
2.3) Extract all files to your Rune factory 5 installed folder.
P.S. You can get the folder on Steam:

For others launchers, just find the folder that have the file: UnityPlayer.dll
2.4- Disable RF5 Config Launcher start before the game:

2.5- Allow BepInEx configure the files for the first time:
Start the game and wait a little at title screen. Only the first time BepInEx will generate all configs files. So just wait a little. The
time depends on your computer specs. And it will not show you any notifications, nothing. Really just WAIT.
After wait a little closes the game.
3) Install the mod:
3.1- Download and open with any zip extractor. I recommend 7-zip
3.2- Extract all the content to the folder:
Rune Factory 5\BepInEx\plugins
4) Play the game and enjoy ;)