Very beautiful art!
I don't consider myself a super good gamer, but I have played through my fair share of platformers and shooters and I could not get past this boat part. I kept dying. I died about 3 times before I just gave up. It was just too long and fighting the same 3 enemy types was getting old really fast.
I need to hear or see feedback (or both) on whether the moonlight attack was working. I know it works because that old lady in the beginning told me, but a sound or visual effect that I'm hurting the enemy would help a lot.
The sword felt useless on the boat. Even if that exploding enemy gets close, it explodes and damages the boat. I think some tweaks to the enemy behavior would make using the sword easier and satisfying.
I wish I could have had more time to get to the parts in the screenshots, but that's all the time I had.