Apologies, that "demo" isn't a demo: I've been using the "demo" functionality on Itch to make sure anyone could download official translations (Japanese in this case). However, it's caused a lot of confusion, and realistically no one is going to need to download the translation unless they've bought the game to begin with, so I'll probably relocate that to the list of game files before too long here.
I should further clarify that the games don't install "on top" of each other: the TRANSLATIONS do, but each game is stand-alone. Only the datacrystal.js file is copied over to potentially unlock some extra scenes, but that's optional.