Neat idea! Got a some nitpicks though:
There's a couple of mistakes on the sprites, the green cucumber enemy loses its outline in one of the pose and yuuto loses his hat's shadow in the camera-facing sprite.
There's also some bugs on the overworld, if you get hit mid attack you can move while the battle starts and change area, but your position is reset when re-entering the overworld.
Statues can hit you with their arrow while you're entering combat.
Also not a fan of how close some traps and enemies are to room entrances, and the sprite's hitbox should be smaller than the whole sprite imo.
Combat was nice and I found a use for pretty much every attack, maybe you should be able to curse burrowed enemies since it's a debuff and not direct damage, also it looks like burning doesn't affect burrowed enemies but I could be wrong.
The fact that enemy attacks only hit their intended target means that you can dodge at the same time with all characters which I don't mind but it does make dodging way easier.
This is subjective but I don't like some of the controls, specifically I don't like having to use the arrow keys for some attacks and items because other than those exceptions that you can play one-handed.
Same deal with the pause menu, it's fine but you should be able to navigate them with the keyboard since it's the only thing in the game that requires the mouse.
I also don't like the slow item/defense/attack menu rotation and how long the victory screen lasts
And speaking of levelling up, the roguelike elements are weak.
There's no equipment or skill tree meaning that character progression is always the same and different rooms don't really matter unless they have traps in them since combat encounters don't have much variation.
It gets samey towards the end since it's pretty easy, but fun demo overall