Hi, I'm sorry for the problem you encountered.
What you can do is go in your PC user folder, then from here go to AppData\Roaming\ClemiNeko\WWB and delete the file named WWB_settings.sol.
This will make the game go back to its default settings so your game will start windowed.
Hopefully this will help. Also can you tell me your screen resolution? This might help to find a fix!