First of all, delightful art assets, from sprites to music this game is a audiovisual treatand i cant stress it enough. Now that thats out of the way lets focus on what should be evaluated for this Jam.
The core gameloop is great, hoping from side to side killing enemies feels responsive and snappy while lining up your shots take skills; other stuff takes more than skill, dodging is heavily reliant on luck, the more enemies in the screen the lesser space to navigate and given that most of the time you have to jump because of a hazard is coming or not jump because an enemy is in the way you cant dodge, making for unfair difficulty, not hard dificulty, unfair.
My fix, I would make the ninja jump towards the mouse, if you want to keep the hold mechanic make the ninja go faster the longer its been hold, that would keep game challenging whilst getting rid of the unfair parts.
That problem aside the game plays like a fiddle, no bugs or quirky behaviour, great feel design with subtle screenshake and flashes and lastly each enemy telegraph in a clear manner.
Theme, only one button and the game wouldnt be the same without it.
Originality, japanese themed walljumping platformer shooter, you bet.
I hope they make a mobile version of it because it would fit the platform well, an almost perfect game this jam deserving of praise.