A few simple things I feel would make this game even better.
1.) A block mechanic; this would force the player to think defense sometimes over constant sword-spamming.
2.) Different hit locations on enemies (and death sequences); again this would force the player to use a bit more strategy.
3.) Different stage environments; I'm in quite a few stages yet the background hasn't changed a bit except for the lower rungs on the towers are now broken (come on, you can do waaaaay more).
With the above elements added, you would have at least a 4-star game for sure.