Elfen Lied by Bernhard HennenEdit
Part of a fantasy novel series that deals with actual elves, each one with a title that begins with "Elfen --- ." The author is German, and the series has only been published in the original German. A possible connection to the works of Lynn Okamoto might still exist, as the manga series is very popular in Germany.
A short work that may have once been a prototype for the Elfen Lied series we know. It had no science fiction or fantasy elements, instead focusing on two musical prodigies, who face the pressures of growing up to overcome their fears and realize their dreams. It was featured as a bonus chapter in Elfen Lied Tankōbon Volume Five and again in a collection of shorts by Lynn Okamoto called Flip Flap. It has yet to be translated into English, but a summary can be found here.
A sexually explicit animation about the adventures of two Elf Princesses as they defend their kingdom, a so-called Hentai piece. It appears to have been named solely to make purchasers think of a connection to Elfen Lied, ala the direct-to-video 'mockbusters' of popular films.