Differences between the Elfen Lied anime and the manga are many, and noteworthy. Like many another manga series, when adapted to become an anime series, Elfen Lied underwent several changes in plot, setting, situations and characters. Each of the thirteen regular episodes, plus the OVA compress the events of the several manga chapters, and are not always in the exact order depicted in the manga, usually owing to the multi-chapter flashbacks. This page can also provide some answers.