This game was made with Unity, and the save file is in the default location. On Windows, that is:
%userprofile%\AppData\LocalLow\<companyname>\<productname>
You might have to enable viewing hidden files to see it. For This game specifically it's:
%userprofile%\AppData\LocalLow\LucasPucas\ShyGuySurfing
If you pop that in Windows explorer, it should bring you there :)