Hey there! Just played the demo and overall had a great time so I thought I would share some thoughts :D
1) The main cast of characters all seem very established and well characterized besides Kanja. I know she is anemic (which is a bold choice since it is so hard to pull off so I am excited to see what you do with it) but for being the main character she is the least excited among the bunch. For a demo you really have to "grip people by the balls" because it is gonna take awhile for this project to come out, so you need it to be as memorable as possible. Kanja comes off as a stereotypical hero which can be disappointing when most of the other characters that were introduced (including the NPCs!) seem so well characterized. I am sure we will learn more about Kanja soon though :)
2) For using a lot of default assets and tiles you did a great job mapping the overworld and shaping characters. While someone who has spent time with RPG maker will instantly recognize the character generator, each character had their own style fitting their personality so well done! Depending on how seriously you plan on taking this project I would recommend commissioning and artist to help bring your world to life that much more!
3) As well done as the overlay of the mapping was, it felt very empty at times. There were so many things around me and I couldn't interact with any of them. When exploring the other dimension I spent time clicking an objects that could have had hidden goodies and was never rewarded for it. As a player I would much rather find items through interacting with the world than opening a red chest for the 10th time.
4) Speaking of the other dimension the encounter rate felt a bit high, and with the exit so close to where we enter there was no reason to do anything but flee most of the battles.
5) The world immersion was really good at times and would completely drop out at others. Early on I was excited and felt like I was going to get tons of sound effects and music (my favorite) but it dropped off rather quickly. Randomly dropping the music for comedic effect was really funny the first time it was done and genuinely made me enjoy the conversation going on, but then it happened a few more times to the point where it felt unintentional. Also the lack of music in such an emotional scene at the end took away from the interesting story point you set up and felt like a sour ending to the demo.
I hope I didn't come across too harsh, I just started working with RPG Maker recently myself as well and seeing the work you put in is showing me how much potential both you and this program has and that I am gonna have to step my game up! Followed you on Twitter and look forward to following your game. Keep it up ;)