Elfen Lied (TV Series)

A humanoid test subject known as a Diclonius escapes from a lab somewhere, protected by some sort of supernatural powers. She literally paves her way through a sea of blood of her own making and falls into a sea after a failed attempt of stopping her permanently with a sniper. A while later, the two cousins Kouta and Yuka comes over a naked girl with a peculiar set of horns on her head standing in the ocean. Without the ability to say anything but "nyu" and looking quite lost and forelorn, the two take her with them to their home, name her... well, Nyu, and let her live with them. What they quickly learn, however, is that some sort of organization is after Nyu. And Nyu herself seems to have another personality within her. Who is Nyu? WHAT is Nyu? And just what is going on?