I also enjoyed the .Hack Sign series of games when they game out years ago.
Although, you may want to check out your local GameStop or online via ebay to get the other three volumes of the series.
If you play the game from Vol 1, you can transfer all of your experience points, level, equipment, and items to each new volume via your memory card.
This makes the whole game quite fun to play.

Oh, and welcome to the boards Garry