Not the game dev but I do have some advice, the files in the game folder are a pretty good tell to what engine/platform the game is made on. Renpy games will have a renpy file for example and unity games should have a unity icon on one of the files in the game folder. This game has a renpy folder so it's made in renpy (or is at least using renpy in it's development process). I don't have an advanced understanding of this but I've played enough visual novels to notice the trend. Not a solid answer but it might tide you over.