The anime ends at Volume 7 and then there are two OVA's that cover volume 8 (with a few liberties taken due to time constraints). The manga gives the real ending and goes up to Volume 17. I have up to 13 and it gets a lot better. The whole show was a flashback but the manga is all real time and has a more fights and whatnot. It isn't exactly deep but it's well drawn, has good fanservice, and the action is sweet.