I really like the aesthetic. It's clear that you put effort into making a cohesive style, and it winds up looking like one of the better games in the jam. The coin collecting gameplay itself isn't bad, but it took me like 4 or 5 runs to figure out where I needed to go to hit 20 coins. I won't rail on the issues with the enemies and NPCs, because you're clearly already aware.
I had a number of strange UI glitches, like the menu selections being offset from the text and sometimes text staying up past when it should have.
It also seems like after a point, your ninja is just constantly sliding forward a small amount, which gives it a floaty feel.
I think this art-style could fit a lot of different game types, and I'd be excited to see you make a more complete game with it.