Nyu is a character from the amazing anime "Elfen Lied" for those of you who did not know. She is someitmes Lucy, but mostly when she is angered, in a way. So its not exactly muliple personalites? Also she was kept locked up a lot of her life, and went through some very bad, and harsh expiriences, including accidentally murdering her friends father and younger sister. Keep in mind folks that she is not technially human.