Download the official Windows setup from https://heavenburnsred.yo-star.com/ Add it as a Non Steam Game Use Proton Experimental Install it where you want (I recemmand somewhere on the "Z" drive) Set the newly installed launcher as a Non Steam game (you can remove the setup if you want) Use Proton Experimental Let the game download and install (it will take some time, especially the installation part)

Launch the game from the launcher and it should works without issue