I don't think he's an antivirus or Kizuna. I think it'd be a little too much if BOTH Zetto and Kizuna were playing as characters in the group, not to mention that Kizuna asked Zetto about "his friend" (meaning Alpha) when he appeared to her once, as if she wasn't friends with him as well. However, I do think that it's possible that Gamecrazed is actually a girl, with the somewhat-androgynous appearance and a couple other hints (not responding much to Nylocke's "Sir Gamecrazed!" and squinting eyes when Nylocke mentioned both of them being manly). I definitely do think that Gamecrazed is in a place where he/she can't leave or put other people at risk, since he/she seems disinterested in revealing his/her true identity, meeting up with the others, or getting involved with searching for a virus. My current theory is that Gamecrazed is at an orphanage or foster home, but there's plenty of other possibilities. Gamecrazed is definitely the player I find the most intriguing at this point, though, and want to know more about.