Lucy - Nyu - Yenra Picture Wiki
Lucy/Nyu of Elfen Lied
Lucy is a diclonius girl, assumed to be fifteen but never explicitly stated (eighteen in the anime), and the central protagonist of the series.
Lucy has vectors with a limited range of about two meters (6.56168 ft). However, she can be swift and lethal within that range, and will use any nearby objects as high-velocity projectiles to kill at greater distances. She is also capable of stopping or deflecting most standard ammunition when she concentrates on the task.
Nyu is a split personality of Lucy that developed after a .50 BMG round pierces the metallic helmet encasing her head when she escaped.
Nyu has a childlike personality and infantile knowledge of the world, and lacks spoken language skills, being able to say only "nyū" and "Kohta" most of the time. As the series progresses she develops a wider vocabulary, by the halfway point she is able to speak perfectly normal. Nyu is innocent and incapable of violent acts, a foil to the normally cold and sadistic Lucy; she is the manifestation of her "good side". When Nyu is attacked violently (or hit on the head), she regresses into Lucy; likewise, when Lucy is treated with love and kindness, or wants to hide herself from Kohta, she will change back into Nyu. While Nyu exists first due to trauma, Lucy subconsciously encourages her presence due to her feelings of guilt towards Kohta and to prevent her from harming him (directly or indirectly).