Sequel, parallel, who the hell cares. It's a new Hellgate game. Also, new games to series are often called sequels. Take YS series for an example, the newer games usually takes place before the farthest timeline and yet these game are called sequels. It's a sequel to the series, not to the timeline. Also, secondary definition of sequel is: "an event that happens after and is the result of an earlier event". Which in this case would be true.
