Nice work! This is a solid entry that with some polish could be really good! I've said it before on other entries, but I always appreciate original artwork in RPGmaker games. It really makes them stand out. I didn't even mind the battles with what appeared to be concept art. It seems a little unfinished, but I can see the vision of where this could be going.
The gameplay was fine, if a little difficult at first. The boss was way easier for me then the basic demons for some reason. My biggest critique is in the writing. I really like the story itself, but the actually dialogue is a little rough and has typos. I assume this is related to time, as this was a jam, but it stood out to me.
And as others have commented... darn! A cliffhanger! Leaves you wondering whats next. Hopefully you'll be continuing this project!