Nana

Nana is one of the most recognizable and beloved characters from Elfen Lied.

She is a young Diclonius (like Lucy) who was raised in a research facility and treated more humanely than most other test subjects. Because of this, she is gentle, innocent, polite, and deeply trusting — almost childlike in her worldview. She refers to people respectfully (often calling people "Papa" if they show her kindness) and has a very pure-hearted personality.

Unlike Lucy, Nana is missing both arms (which were severed during an earlier incident), so she relies on her vectors (invisible telekinetic "arms") to function in everyday life, and she uses them very openly in front of others since she doesn't try to hide her nature.

She's frequently portrayed as the "pure" counterpart to Lucy's darkness — cheerful, loyal, emotionally fragile, and desperate for a real family and a peaceful life. Her innocence and tragic backstory make her one of the most sympathetic characters in the series.

(Short version: sweet, armless, vector-using Diclonius girl who just wants to be loved and calls kind people "Papa.")