Hi there! It seems you have a corrupted save file. This can happen if the game is closed while saving, or if the savefiles are manually modified, amongst other things.
You'll need to find the corrupted save file located in: Users/<YourUser>/AppData/LocalLow/Bura/Long Gone Days and delete/take it away from that folder. If you have more than one savefile and you don't know which one might be corrupted, try taking one of those savefiles out of that folder and see if the error persists.
You won't be able to save your progress either if there's a corrupt savefile, so doing this is necessary to play the game.