After escaping from her prison in a bloody rampage, murderous diclonious Lucy is shot in the head. She survives, but suffers brain damage, causing her to become harmless and baby-ish. Two university students find her and decide to take care of her, naming her "Nyu".
Lucy/Nyu is a Diclonius, a species of pink haired humanoids that have horns protruding out of their heads and powers including vectors which are invisible hands. One night she escapes a facility were she was tortured and experimented on, when she gets shot in the head she develops a personality named Nyu were she acts cute and childlike and then meets Kouta.—Breanna