While time line wise this was a sequel, but it's basically a series just in the same story world. There are a few familiar faces, but the story line is completely different. Although there is one GREAT cameo.
For once, I have to comment on the main character. I found her to be entirely useless and while she had some definite character depth, I just didn't like her. Think of Sakura from Naruto, and you'll get an idea.
There were only a few characters that I felt had a great level of depth to them, which actually gave the story the depth that it had.