Elfen Lied

Lucy was born a Diclonius, a human variant with horns and invisible telekinetic arms capable of tearing bodies apart from a distance. She has spent much of her life confined in a research facility, subjected to experiments and isolation, and when an opportunity to escape appears she leaves a massacre behind her.

During the breakout she suffers a head injury and develops a childlike personality with barely any speech. Kouta and Yuka find this wounded girl near the coast, call her Nyu, and take her into their home without knowing she is the same fugitive being hunted by the government. As researchers and Lucy's violent past close in on them, buried memories begin resurfacing, revealing that her connection to Kouta started long before their apparent first meeting and carries a tragedy neither has fully remembered.