This arc begins with the bloodyescape of Lucy from the Diclonius Research Institute, and the efforts directed by Kurama to get her back or kill her. It continues with the amnesiac Lucy found at the beach by Kouta and Yuka, two cousins and childhood sweethearts reuniting after a long absence. With Lucy rendered childlike by wounds taken during her escape, the pair brings her to Maple House, where conflict emerges over both the actions of Lucy, now called Nyu, and Kouta's amnesia regarding his past with Yuka.
The legendary Special Assault Team is sent out to capture or kill Lucy, with the eager Human killing machine Bando at the forefront of this effort. When Nyu/Lucy runs off, Kouta and Yuka find her at the beach, only to be knocked out by Bando as he captures Nyu. Bando makes the mistakes of dismissing the threat Lucy poses and pushing Nyu until her personality reverts to the more vicious one. Bando is savaged and humiliated. Nyu returns to Maple House, where a Kouta now suspicious of the Kamakura police awkwardly tries to change her wet clothes. The end of this arc introduces Mayu, who saves the wounded Bando, and the concept that Lucy is not the only horned girl. Mayu's dog Wanta is unnamed but also appears.