This is a raw scan pretty much, right? (Pretty good at that, too). To increase contrast you can use any image editing program, but if you have photoshop or GIMP I would recommend playing with the levels and value curve functions for greater control.
Ya your right about the scan. I have to admit it was an old drawing before i got to scan it but i do need to increase my contrast like Talo said with my basic drawings.
It's very nice, I like the detail's on the throat and the hair. It could be a little darker, and could use more work on the shadows. It's a pretty common anime piece, but it's nicely done.
Thanks for the comments and if you don't know who Kazuo is (firetail) he's a character from a manga Battle Royal. It was a book first and is also a live action movie to.