Very nice concept....buuuut....
Overall, I really did enjoy this game; there was enough variety between each game to keep them all unique yet interesting, and even if it was repetitive, that was easily overlooked.
I do have one suggestion that might improve on of the games, though:
In the game where you fend off against Ninja warriors wielding katanas, I found it quite easy that the ninjas ALWAYS used swords. by simply always moving, and swinging my own katana, i rarely had any chance of being hit.
Perhaps adding in ninjas who specialize in throwing stars might add some degree of difficulty? That way, they could hit from a distance, and you would be forced to use your wits, and even the guns, to get to them first.