Author's Response:
Well, the grin is because he's insane (psycho, psyche, psyche ninjorb)
Hole in the chest because shit happens. I may make a prequel and shows how that happened and all of the back story.
And about the naruto, I have only seen like 4 episodes of naruto, and you're the one who has watched too much because you have seen so much you know if someone is doing something similar to it, which this is not. Also Naruto isn't the first show about ninjas.