Wow I really like the artstyle! It's rare to see both 3d and 2d done very well. Very good atmosphere and cute drawings that really felt integrated. This one really could use full screen button.
I also did a turn based game and I know it can be hard to explain all the systems. It seem like you impemented a lot of things, but honestly I just chose the big attack each time lol. Also I'm not sure I figured out the dialog system - sometimes I clicked through it and nothing would happen.
I did finish it and it kinds of just ends, which make sense because you mention it's a demo. Could be cool to explore with a little more polish :)