With an opening secretly provided by Professor Kakuzawa, Lucy escapes the Diclonius Research Institute amidst a slaughter; during the escape, she is struck by a high-caliber shell that she survives, but renders her amnesiac. Mayu is raped by her stepfather; finding no help from her cruel and heartless mother, she flees and becomes homeless, eventually finding a puppy she names Wanta.
Kouta and Yuka reunite in early spring of that year, with the amnesiac Kouta disturbing Yuka with his lack of childhood memories. On the beachfront, they encounter Lucy, rendered childlike as a result of her head trauma. They resolve to take her to Maple House, where Kouta will be staying at while at college. After some mishaps and misunderstandings, Yuka comes to dwell there as well. They come to call this version of Lucy 'Nyu'.
The Special Assault Team makes an unsuccessful effort to retrieve Lucy, leading to the maiming of Bando, one of its top agents, who swears revenge. This battle is witnessed by Mayu, who aids Bando and who first contacts Kouta and Yuka as a result. This is the first of many occasions on which Lucy and Nyu switch dominance of their shared body.
Kurama sends out Nana to try and retrieve Lucy, which ends with Lucy dismembering Nana and the temporary disabling of Lucy's vectors. This battle is witnessed by Mayu, who later on believes she may have hallucinated it. Mayu almost loses Wanta to a woman claiming to be the small dog's true owner. After some initial concerns about her hosts, Mayu accepts their invitation to stay and live at Maple House.