Elfen Lied's story presents a fictional species, the Diclonius, a human mutation with two small horns like the ears of a cat. The anime's opening theme song is "Lilium" by Noma Kumiko and is sung in Latin. The ending theme song is "Be Your Girl" by Chieko Kawabe.
The story begins with a young woman named Lucy, escaping from a research facility on an island off the coast of Kamakura in Kanagawa Prefecture, Japan. Unarmed and naked, except for a metal helmet that concealed her features, is able to leave the premises after dismembering and killing several guards and employees using a kind of supernatural powers.