Really awesome :D
Didn't get to finish it yet, but I love the VN sections so far^^
Since it's a demo it comes with a few minor bugs:
The mirror image in the first scene with Quentin starts with the wrong sprite for her.
Even if you are already on the same floor, pressing the button will start the elevator again. (necessary, because it's unloading when entering the elevator?)
If you exit the elevator and then reenter and press the button of the same floor you're on, you'll end up at the "next" floor.
The colors for the white and black button are flipped inside the elevator compared to the elevator button UI
Using the menu while standing in front of the elevator (and maybe in other interactable places) will actually interact with things (like make you step into the elevator.)
Also, you might need to consider tweaking combat a bit. I'll focus on Quentin's world and the combat there for this example:
As far I see, if your time top left hit's rock bottom, you start a 10 second timer to get back up, before you lose. Your time is reduced both with inverted Quentin cards and by "redrawing" your hand. Redrawing might be necessary, because the main skill of the enemies is to permanently lock your hand cards from being used. But you of course can't redraw, if the time is already at 3 and the 10 second countdown is ticking. You're basically done for at that point. When playing normally you might avoid using the inverted cards, because of course it would be bad to loose time, even if you can regain it with the one or other right oriented card. I lost maybe 7 matches (including a reload from autosave) and won 2 or 3 by playing "regularly" with just Leroy's and Quentin's cards.
But then I figured out a way that completely breaks combat, which you might want to consider "fixing": Press all arrow keys at once at the start of the battle and keep them pressed: You'll automatically use all cards, no matter what they are, hold or regular. It is impossible for monsters to "lock" card slots that are empty (because cards come in one at a time), even if you end up at the final countdown, chances are, you still have enough cards coming in to get the time boost you need (I rarely fell that far down though), or if they lock, you have enough time left to unlock them again via redraw and then boost back up. Similarly the battle with Primadonna, the one slot from which you played the inverted bomb stays "unlocked"so you can just play until you get a regular bomb to unlock all slots again.
Both cards have a synergy, since Quentin would need the unlocks and Primadonna would need the extra time, but this "easy" workaround right now makes it obsolete.
It might be a bit harder to find the right balance there, but maybe if you actually locked the slots instead of the cards that would help with some things. Also, maybe I missed it, you could hint at the necessity for Leroy to go "explore on his own" to return to the hub, so people are guided to meeting all characters/getting all types of cards first, before tackling the more intense fights.
Good luck with further development :D