Yeah, Fluegel is the main villain of the manga. Suspecting that since the .hack series usually game-izes everything, we'll see a .hack//LINK series as well.
This is Kite.
It's not the Azure Brigade as seen in GU--this is the real Kite, not a copy.
As far as who his friends refer to, I'm unsure. I know Tsukasa has one, which is causing her/him to act weird and concern Subaru.