Uhm. Yeah. That's a prototype. A prototype of the fighting mechanics of a game.
We shall see, how that turns out. I would not worry about "copying" some game mechanics. There is not that much mechanics to create a minigame or mechanic to chose from. You are bound to copy something (pun intended).
Though the turn based flavor does not necessarily go well with the rythm game arrow punching. That's action game mechanics, not adventure role play mechanics. Of course it can be mixed in, to loosen things up (yeah, I can't resist). It really depends if this is a main mechanic or just some side mini game for fun.
Also consider having multiple keys down the road. Like wasd. And subtly telling players what to do ;-)