Making the game automatically load the overlay on the game start
This is a different method to start the overlay: with this one you don't have to manually start the injector every time you start the game and you don't have a whole additional process and window running. It should also help people for whom the default injection method doesn't work.
This one requires you to edit the Tekken executable and make the Overlay a dependency of Tekken, so Tekken will automatically load the Overlay as its dependency each time you run it. You will need to repeat this process once every time game's executable is updated: not every game patch, but almost every.
Install it.
Copy the contents of the Tekken Overlay folder into the folder where TekkenGame-Win64-Shipping.exe is located: ...\steamapps\common\TEKKEN 7\TekkenGame\Binaries\Win64. You can quickly find out this folder if you open Tekken, open Task Manager, find the TekkenGame-Win64-Shipping.exe in the Details tab, RMB on it and choose the Open File Location menu. In the end it should look like this:
Make a backup of your TekkenGame-Win64-Shipping.exe in case something goes wrong and you need to recover the original.
Open the Explorer Suite. Its alternative name is CFF Explorer. Open the TekkenGame-Win64-Shipping.exe file in CFF Explorer:
Go to Import Adder tab, press on the Add button and choose the tekken-overlay.dll file:
Select DllMain in the Exported Functions list and press on the Import by Ordinal button:
Press on the Rebuild Import Table button:
Open File menu and choose Save menu:
Press Yes button to confirm overwriting the file:
Now Tekken will automatically run the Overlay each time you run the game.
Video demonstration of the process in case anyone is having issues following instructions in text with images.