Everyone else is already praising this game (well-deserved, it's great and almost certainly one of the best-made games of the jam), so I'm just going to list my complaints and suggestions so y'all can make it better moving forward.
The controls are a bit stiff. I'd recommend adding some acceleration and deceleration to make the character feel natural (or if there already is some, tweak the numbers a bit). More fleshed out animations and sound-effects would help tremendously as well.
The blur effects on sword swings are nice, and I think adding an after-image to the dash would pair nicely with the other effects. Speaking of the dash, I think it's a shame that if you're swinging your sword and try to dash in the opposite direction, you dash forward instead. I'd like the ability to swing your sword and then dash backwards to avoid an enemy attack.
As for the enemies, I'll cover both. The skeletons honestly should not get staggered by every attack. For an introductory level of a full game it's reasonable to have easy enemies, but as the only basic enemies in this game, they're incredibly boring to fight. The boss is much better, though the arena detracts from the fight. The boss design seems like it would fit better in a flat arena, or one with a single platform.
Other random suggestions include a diagonal dash, dashing through enemies, and cancelling attacks with dashes. Honestly I just really love the dash: it makes this game stand out so much more than the other side-scrollers in this jam, and if paired with some more difficult enemies, this could become something really special. Props.