Very good job with the game!, I really liked the art, music and the maps, specially Shiori's one, it felt straight out of a first person dungeon crawler, I would love to see more of that style.
I enjoyed the different boss mechanics for every level, and while I don't think I can beat level 5 I quite enjoy its inclusion.
The only suggestion I can think of is to have enemies give some kind of feedback that they are hit, I didn't know they could be damaged so it took me a while to figure out what to do against Shiori.