In .hack/ Legend of the Twilight mostly all of the charaters have a back story in the charaters. Sorry if i am talking about the anime and manga i just wanted to speak in gerenal. Now Ouca is friends with Kaz aka BlackRoses (old one) and they all know mel aka mierielle's mom. ( trust me you have to watch these series 2 times to understand it fully.) Now the plot is a new threat is coming back to the world forming what the orignal .hackers would call Twilight. If you ever read the Novels Another Birth then you would notice that the charatersin this series are the same or almost the same. I am really sorry but this anime makes you think while you enjoy it. Each story interlocks with a different series. Sign/ Another Birth, Another Birth/ Legend of the Twilight, G.U./ Roots.