I'm feeling a bit of Undertale with the cast, and a lot of Zelda in the gameplay. I like the charm of the game; the theme is a funny twist. I also liked the ending, having to choose between the four souls made me feel clever when I had the clue to choose the right one.
Most of my critisisms are mechanical, which is a difficult thing to gives notes on since I'm not sure how BGStudio works. Others mentioned the hitbox issue, I also noticed that the player avatar slides a little more than the controls warrant. This is a bit tricky since in old-school pixel adventure games a la Zelda the tightness of the controls is pretty important, since the boxy dimensions of the pixels force the player's movement to be precise.
Also, because death brings the character back to the entrance of the room, I used that to teleport myself quickly back through rooms by dying intentionally. Lots of games have a fast back-tracking mechanic to help the player not have to repeat ground they've already travelled, but in this case I wasn't sure if this is intentional. It's not a big thing, I just thought it was kind of funny.
In all, it's a wee game but every room and enemy feels like it/they have a purpose. Good job. :)
EDIT: One thing I forgot to mention, I'm not sure if this is possible with GBStudio, but I think this game could really benefit from a diagonal movement mechanic. Being restricted to compass positions can make navigating feel cramped at times.
EDIT AGAIN: Alsooo, it could use a little bit of musical variety. Maybe having a more dramatic/climactic song that comes on after you give the sword to the Demon and get access to the soul room? Just something to give some narrative context through the audio.