Great, but something doesn't seem quite right.
Even though the action sequences are perfectly executed (literally), the story is extremely well conducted and there aren't any flaws in the actual graphics, something seems missing.
Maybe it's all of the Ninja's allies dropping like flies, I dunno.
But the Ninja does seem extremely emotionless. His reaction to John's death, aside from his resignation (which likely would have happened anyway, since the events taking place veered him off the army's course), wasn't that intense at all, and seeing as that was the only person he ever apparently connected to, that's a whole lot of emotion that isn't there.
Considering that this is the protagonist of the story that we're talking about here, he shouldn't be just a machine of violence. Even in Madness-style animations.
But this emotionless outlook of the Ninja's makes me wonder how he got a friend like that in the first place. If he's such a killer to the core, how did he develop such an intimate and lasting friendship? (I mean intimate as in close. That's all. Unless you were planning otherwise.) He seems like the guy who would rather clean his firearms than go out for a night of fun and socialization, you know?
Or am I just taking this too seriously? Really, it's up to you where to take this. I'm just noting that something here is a bit off. Either he has some deep feelings and reacted way too lightly to the long-term-affecting tragedy (Keep in mind that we're talking one death, not a million), or he's just a tool of destruction and that the friendship seen here shouldn't be here at all.
Up to you.