Anyway, .hack//GU is the second series of games released in the .hack universe. In this world people are drawn to the popular MMORPG called "The World," and the many mysteries surrounding it. Although most players of The World simply see it as a game and pass off the strangeness as just rumors, the main characters themselves find themselves wrapped up in these mysteries and see the truth for themselves. Thus the real story begins.
The original .hack series was told across multiple forms of media, and focused on multiple characters. The Novel AI buster focused on a system admin who deleted rogue AI (AI that strangely developed their own personalities), the anime .hack//SIGN introduced us to the strange "Tsukasa" as he finds himself unable to log out from The World, and the original game series focused on Kite as he investigated why his friend Orca fell into a coma. These stories are each a small piece to a much larger overall mystery that's at the center of The World, but I'm going to avoid spoiling it. The reason? Because the original .hack storyline will actually be included in .hack//GU Last Recode.
.hack//End of The World is a special movie that was originally released with GU Vol 1, and will be included in Last Recode. This special completely retells the story of the original .hack games, while also explaining other key events that happened "off screen." It explains the history of The World, it goes into Kite's struggle, and it even tells of the events leading up to the start of "The World R2" and the entire GU series. For the most part this special includes everything you need to know to jump into GU, but even then some details will be lost.
Although GU is a brand new story of it's own, many characters from the past do find their way into the new story. One large focus of the .hack series is actually on the players of The World, and how they change over time -- this can especially be seen in GU where many years has passed since the original series. For example. the main character of GU, Haseo, was once a troll player killer seen in .hack//SIGN; however, the events of SIGN greatly changed who he is today, and he returns to The World without the memories of who he once was. Other characters from the original .hack series also undergo major changes, but even without knowing their pasts it's easy to understand the struggles and hardships they have faced.
The only thing not included in Last Recode is the anime series "Roots." This series is the start of the GU storyline and shows Haseo as he logs in for the first time, and it also shows the events that lead up to him becoming known as "The Terror of Death." The events shown in this anime is a major driving force for Haseo to continue playing The World R2, and without seeing it for yourself the start of GU can be quite confusing. While it is possible to get by without it, as the basics of what happens is explained in game, it's recommended that everyone tries to give it a watch before starting the game. Sadly Roots is a bit slow on it's story telling, but the pay off is well worth it.
While there are other stories within the .hack universe, and I personally recommend checking them ALL out, they aren't needed to understand or enjoy GU. Again GU is very much it's own story, but knowing as much as possible about the past will help. The .hack universe is a very developed one, and GU is only a small part of a much larger picture. It's a great place to start game wise, but there's still quite a bit you can go through before then.
