Awesome start for a piece! I really love the way the hair flows, and I'm looking forward to seeing how you work with that in color.
As for critique, the nose has already been mentioned - it's very minimally drawn, which may be what you're going for... and if it is, I'd love to see how you handle /that/ in color and shading as well! Regardless, though, I almost think it's on too much of a slant. Putting it more upright (or perhaps defining parts of the nose that aren't so slanty) would probably be a great help.
Also, one little nitpick - the Konoha symbol on his forehead protector is backwards.