Clip Studio Paint belongs to CELSYS (https://www.clipstudio.net/en/)
I do not take any liability for any of the forks done from this software; no reverse engineering, disassembly or decompilation was done.
This software works as an overlay and sends inputs to your PC, emulating both modifier and arrow keys.
"Full Focus Mode", shown with a tablet icon, puts Clip Studio Paint on a "menu-less" mode, changes your Windows Settings for your taskbar's auto-hide while the mode is on and shows you a timewatch in case you want to keep track of your time without un-hiding your taskbar.
As a note, this app will always be in the middle right part of your pc, no matter if you're on Portrait or Landscape mode, and it can be hidden as you wish. This app also has a special function that, if used as a button action, you can open or close the app with it.
Just decompress the file into your system. If you see any error about redistributables or it doesn't fully load, remember to install those from Windows themselves.
It's recommended that you launch this app when you click your pen's button (https://support.microsoft.com/en-us/windows/change-pen-settings-a53cd80e-4f89-ae30-d6da-389d630d89a3) but you can also do a shortcut to this app if you want.