There aren't achievements per say in this game, but I did achieve the rank of Master Ninja on chapter 8. I played for a while today, it was rainy and cold out so I didn't do much else but game and go to the gym.
I completed chapters six, seven and eight on normal difficulty. The game is a blast, not too hard not too easy. It's going to be hard to top this game on the ds for me, unless GTA Chinatown wars pwns.