Watch Elfen Lied: Tooriame nite Arui wa, Shoujo wa Ikani Shite Sono Shinjou ni Itatta ka? - Regenschauer Online

Having been accepted into the Kaede Inn, Nana struggles to find some way to contribute, though she inadvertently brings more trouble than assistance. However, Nana's worries are directed more towards fellow resident Nyu, whom she had only known as Lucy, the violent Diclonius. Fearful that Nyu will unleash the same horrific savagery—violence that scars Nana to this day—upon those close to her, Nana faces a dilemma: attempt to live peacefully alongside Lucy with all the uncertainty that that entails or dispose of the source of her worries, shattering the relationships she has formed at the inn. As Nana struggles to come to a decision, Nyu recalls a painful memory of one of her dearest friends and one of her greatest rivals.

The "diclonii" (singular: "diclonius"), otherwise known as a two-horned human, are mutants of the human species, may well be the next step in human evolution. The diclonii have horns and strong telekinetic powers represented by arms. However with this great power, they could easily destroy the human race. Fearful of their power, humans quarantined the diclonii into secret research facilities to study. However, in a freak accident, a enraged female diclonius escaped, killing many guards in the process. Interesting enough, the female escapee appears to have suffered amnesia after her escape and floated to Yuigahama of Kamakura city. There, she meets two people named Kouta and Yuka, who name the female diclonius "Nyuu", and decide that they all should live together.