I have played this demo for around 30 minutes, and I gotta say this is a really cool game!
The gameplay works very well, the levels are well-built and you don't spend hours stuck on a puzzle. The three-character dynamic is interesting, as each character brings something different to the table. Finally, the graphics are very nice, they have a nice cute style that works fantastically in this small screen size! The fact stages also have a lot of hidden gems will probably make for a nice replay value.
On the downpoint, I would put Rosa's sword reach which is rather small and I ended up colliding with enemies I was striking more than once. I feel that range is quite hard to read, but that might just be me?
I'm also not a fan of how Wendy sticks to the ground underwater. I understand it is to make a difference between her and Izzy, but it feels strange that a character that can swim cannot move once she touches the ground...
As for the graphics, I truly enjoy most of it except the font that I feel is a bit hard to read (probably due to the dithering) and the boss' sprite in the water/ice stage (second stage of the demo), which style clashes severly with the rest of the game screen. Is this sprite final?
Other than that, the rest is quite franckly really good and I can't wait to see the final game! Congrats!