I installed quartz and ffdshow, but the below mentioned crash still persists.
To be exact, the crash happens outside the Zelcova shop, after the line by Hiroki "I honestly remember having to treat you guys when we came here more than the taste of their cakes", the story then enters a flashback about the high school times. The crash will happen wherever inside this 7-line long scene.
Maybe it's because I am on Proton Experimental, but the previous reports didn't reveal the exact proton version they ran, so I also didn't try switching to another one.
I ended up finding a windows machine, skipping the flashback scene, initiating a quicksave, and then loading the quicksave on my Linux machine to continue playing.
I put my quicksave file here: Google Drive Share
Tweeks are optional
You can press ESC to skip OP&ED if not install quartz and ffdshow.
I tried install them, but it will get stuck on OP&ED on my PC.
So don't need protontricks
protontricks 386970 quartz ffdshow next next finish on the wizard and it works without crashing
The game crashes after playing an hour. It doesn't matter if quartz and ffdshow is installed. I think it is because the game wants to play a cute scene.
Performance is good and everything works. Though you need to install quartz and ffdshow through winetricks to get the mpeg videos to play.