Although the opening theme song for this anime starts out very gentle and beautiful, the beginning of this anime is dark, bloody, and violent. Elfen Lied starts out with a bio-engineered female robotic weapon breaking free from its restraints and escaping from the laboratory that it has been kept in.
This female bio-engineered weapon is completely naked, and during her escape she brutally kills anyone who appears before her. She rips off heads and limbs, and blood flies everywhere, so the deaths are violent. There is a lot of nudity, blood, gore, and violence in this first episode, and since there is a military element to this anime, I do not recommend this anime for young children or those under 12 years of age. Older teens may be fine with this anime, but this is definitely a mature anime.
The bio-engineered weapon can levitate objects and throw them at others to kill and maim them. She can rip off body parts without touching them, so she has super human capabilities.
The female bio-engineered weapon is able to get outside of the lab leaving a trail of dead mutilated bodies behind. However, she is shot in the head by a sniper, and the gunshot wound causes her to fall into the ocean. The violence in this anime ends here.
After all that action, this anime then moves towards everyday life events, and it looks like any normal anime. The scenery and graphic images are beautiful in this anime. The nature scenes remind me a lot of the imagery in the Studio Ghibli films. The greens and purples are stunning. The vibrant coloration is like a painting, and they alone make this anime worth watching.
Now we are at the middle of this anime, and it starts as any normal anime would with normal everyday people wandering around Japan. There is a woman named Yuka, and a man named Kohta. They are the main characters and they are cousins. They meet for the first time in a long time near the train station, since they will be going to the same college together. They both spend this first day reminiscing about their childhood adventures together, and revisiting places that they loved as kids.
Yuka and Kohta decide to help her by giving her Kohta's clothes to wear. Something about her reminds Kohta of someone scary from his past though, so he is uncomfortable with her. Nonetheless, they both still decide to take her to Kohta's new home, which is very spacious and beautiful. The house used to be a Japanese-style inn, so there are numerous rooms, and there is even a garden. The house actually belongs to Yuka's family, but her mother is letting Kohta stay there rent-free as long as he cleans the house and maintains it.
While Kohta is shown around the house, we can see more of the bio-engeneered weapon's new personality. She walks awkwardly like a child who is learning to walk for the first time; she cannot express herself or what she needs physically, so when she has to go to the bathroom, she does not know how to say it, so she ends up wetting herself and peeing on the floor. It is during this moment that Kohta comes up with a name for her; he names her "Nyu".
Perhaps Nyu does not feel threatened by Yuka and Kohta since they were not the people experimenting on her, so she does not feel the need to use violence. Around them, she has adopted a completely innocent and child-like persona. This side of Nyu is quite shocking compared to the violence that we saw from her at the beginning of this anime, but it is also a sweet contrast.
Unfortunately, poor Kohta has to clean up Nyu's little accident while Yuka bathes her. Afterwards, everyone sits down to eat, and Nyu learns how to hold and eat rice balls. Kohta is very kind to Nyu and treats her like a little sister. Nyu also seems genuinely happy in this moment; it is hard to believe that she is capable of extreme violence.
Elfen Lied then shifts from these cute easy-going moments, back to the bloody scene in the laboratory that Nyu escaped from; this is a reminder of what Nyu really is, and what she is truly capable of. It is also here that we learn that Nyu's name in the lab was Lucy, and that the laboratory wants to kill her, so they send a highly skilled sadistic shooter assassin after her.
This anime then returns to focus on Yuka and Kohta, who are sitting in a room together. Kohta tells Yuka and Nyu about his little sister Kanae who died of disease. He shows them the last memento from her, but Nyu does not realize that this object is important, so she breaks it in half and Kohta snaps; he yells at her and tells her to leave immediately; he kicks her out in the middle of the night, which upsets Nyu, so she runs outside blindly in the pouring rain crying intensely.