The arc tells the story of Yuka coming to terms with the fact that Kouta has no memories of their past childhood together, and the pain it causes her to realize this. She ultimately comes to a conclusion, based on inaccurate statements from Kouta, that his amnesia springs from the trauma of losing his family to an unknown killer shortly after their last meeting. Based on the comical efforts of the childlike Nyu to aid the ailing Kouta and on Kouta's continued awkward sexual encounters with Nyu, Yuka decides to move into Maple House.
Kurama tells the wounded and incredulous Bando that he must undergo castration because of his encounter with Lucy, an idea Bando fiercely resists. Kurama sends Lucy's fellow Diclonius, a girl like a daughter to him, to kill Lucy. Her refusal to do this turns the mission into a scouting mission, still presenting a danger to the unworldly Nana.
Mayu and Wanta journey to Maple House and return Yuka's property, left on the beach the night of the battle between the SAT and Lucy. Kouta and Yuka question her but also offer her room and board, though she bolts from the house nervously when asked personal information. During the midst of this, a blow to the head once again causes Nyu to become Lucy, who stops just short of killing everyone when she realizes Kouta is among them. Departing suddenly, Lucy is later found by Nana, and it is certain conflict will follow.