Elfen Lied (エルフェンリート Erufen Rito) is the title of a Japanese manga series originally created by Japanese author Lynn Okamoto as well as a TV anime series based on it. Elfen Lied focuses on a mysterious and deadly breed of horned humans called "diclonius", and the havoc they wreak upon humanity. The title Elfen Lied is German for "Elf Song" (see Lied), and pronounced approximately ['ˈɛlfən liːt], although the correct German spelling would be "Elfenlied".

Elfen Lied first began as a manga series, serialized in the magazine Weekly Young Jump and published in Japan by Shueisha, ending at the completion of the twelfth volume. An anime adaptation began airing in Japan on July 25, 2004 while the unfinished manga was still in production. This caused the anime plot to differ in some ways from the manga plot. A bonus OVA episode was released on April 21, 2005 giving some more background information.

So far, only the anime series spanning 13 episodes and the OVA have been licensed in the United States, by ADV Films. ADV Films said the series was one of their bestselling and "most notorious" releases of 2005. Elfen Lied and the character Nana were the inspiration for the popular Clone Manga fan-webcomic "Nana's Everyday Life" which has been completed and fully translated from English into 6 other languages.

The story begins with a naked young girl named Lucy escaping under odd circumstances from an insular research facility off the coast of Kamakura in the Kanagawa Prefecture of Japan. Lucy manages to nonchalantly dismember and slay a fair number of the staff and guards with a form of seemingly supernatural power and gets outside. A sniper is seen trying to shoot her, only managing to ricochet a bullet off her metal helmet. Lucy then falls off a cliff into the sea, bleeding from her head but ultimately surviving and evading the research staff.

A diclonius' "vectors" take the form of long translucent or invisible arms.

Lucy is not a normal human but rather a diclonius: a mutant variant of humans with two small horns on their heads (hence the name diclonius) that resemble cat ears. The diclonius race possesses telekinetic powers through use of their "vectors", invisible arms that they control with a number and length of reach depending on the diclonius.

The day after Lucy's escape, a boy named Kohta arrives at Kamakura to meet his cousin Yuka. Kohta has come to study at the local university and has been given lodging at an old, family-owned inn, the "Maple (楓 Kaede) Inn", provided he acts as the caretaker. After meeting with Yuka, they go for a visit to the beach and find Lucy washed up on the shore, still naked and bleeding from her head. The head trauma Lucy experienced causes her to develop a split personality. In stark contrast to the cold and sadistic Lucy, this personality is completely docile, harmless and is incapable at first of saying anything other than "Nyu". Not knowing what to do with her, Kohta and Yuka take her back to the inn to look after her and name her "Nyu". Yuka quickly decides that it will be best that she also live at the inn.

Kohta, Nyu, and Yuka begin settling into their life at the inn and Nyu begins to dredge up painful repressed memories from Kohta's past. Meanwhile, the researchers from the laboratory where Lucy was held begin searching for her, dispatching both human and diclonius agents to hunt her down.

- From Wikipedia