ozawa_tomohiro
Artist. A.K.A. "Zack" (penname), "gock" (Pixiv).
Japanese name: I couldn't find it, but according to his home page it's romanized as Ozawa Tomohiro (there are like 15 ways of writing Ozawa and more than 30 for Tomohiro).
See also:
- Home page: http://zack-world.com/
- Pixiv account: http://www.pixiv.net/member.php?id=233268