This game is really fun! I could see myself spending quite a bit more time on the endless mode. You've got great pixel art and animation, a well implemented story, and excellent music! I feel like both characters are pretty well balanced even if the samurai felt overpowered at first.
My one biggest criticism is that the notes that appear at 1 and 2 o'clock on the circle feel nearly impossible to react to when a new circle starts. At first I thought the marker from the previous circle was previewing the next, and when that changed color I didn't have time to react to it. This is where the majority of my damage came from. I'd say if you can get a preview of the next cycle appear after the indicator passes 6 o'clock it'll help a lot.
Amazing job!