Create a desktop shortcut to HorizonZeroDawnRemastered.exe and add -culture=ja-JP to the Target field. This is the closest thing to a "rune launcher link."

Right-click on in your Library. Select Properties , then go to the Language tab.

Highlight the game icon on the home screen, press the Options button, and select Manage Game Content to see and download available language data.

Have you fixed your language pack issue? Let us know in the comments which language you are playing in.