I have been trying to get special k to work on Nioh 2 using these instructions Local (game-specific) | Special K - The Official Wiki but the game won’t launch.
Had you tried global installation? (using SKIF) . Wich version of windows are you using? If WIN7 SpecialK wont work.
Also the latest February 5th build from the upcoming WIP version might be needed for compatibility if you aren’t already using it.
It’s from the Discord channel but it’s easily missed if you just check the forums here a bit or use the main download for SKIF and the release of 0.11.1 of SpecialK until this next version is fully release ready and replaces it.