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".
Kohta takes Nyu in with him while Yuka decides to move in with them. Yuka reminds Kohta of a festival he forgot about, which he remembers ended in a vague tragedy. Meanwhile, the offshore facility sends a friendly Diclonius named "Nana" to find Lucy.
Kurama asks Nana to find Lucy with her powers of Diclonius. Yuka realizes Kohta does not remember his father died in a car accident or that they went to a festival together as small children. Nana finds Lucy.
Kurama remembers his past. After graduating college, professor Kakuzawa offers him a chance at top secret research. While at the offshore facility, Kurama witnesses first-hand the terror of the diclonius.