Wow. I don't know what to say here that hasn't probably already been said, so I'll just say it all.
This feels like a demo for a legit real genuine $20 steam game I would consider buying. Even with only the one fight we get characterization for the heroes, a combat system with depth with a really well done tutorial explaining it. The one fight we get is really well balanced too! I was left with just one hit point to spare before backup arrived even in spite of my lackluster turn based RPG skills (probably a calculated thing, but still impressive).
The only thing I didn't quite get fully was the stunning mechanic, I think I figured it out eventually but the numbers didn't always match up with my expectation. Maybe if we had some more fights I'd eventually suss it out though.
I guess I'd ask that you don't make allusions to other games in your tutorial with a iykyk, since anyone who sees this might actually want to seek it out to get more of what you've cooked up, especially since it's apparently niche.
And I somehow got that far without complimenting the adorable artwork and presentation! The cardboard and paper aesthetic is so well done, it looks extremely lifelike and leaves an impression. I also love you added a freecam afterwards so we could see a bit more of the magic behind it all.
I don't know how you pulled this off in four days, I just ask that you don't stop making games pretty please with a cherry on top!