Please Note : These arc titles are not official and do not appear in-story. These are compressed digest overviews of major events from the series. More detailed chapter entries are also available.
We meet Anna Kakuzawa, youngest child of the Chief, who willingly underwent a transformative operation that gave her a monstrous body but also powers of calculation so vast and thorough, they border on the precognitive. Despite this, there is information she has that her father continually ignores her pleas to hear, though he does depend on her ability to plan his elaborate schemes, and he acknowledges his debt to her for this.
At Maple House, it has been six months since Mariko's death, and among other changes, Nyu has gone from childlike to young adult in personality, Nozomi has moved in, and Nana has daytime charge over their home.
Arakawa enters into a competition to find Lucy with the loathsome Unknown Man while feeling some recriminations over aiding Kakuzawa in spreading the Diclonius virus, whose effects have begun to show in the local population. Arakawa also has awkward encounters with Kouta, the last of which leads to her finding the location of Maple House.
The Unknown Man sacrifices and horribly abuses an innocent Silpelit in an effort to locate Lucy, instead finding Nana and Mayu. Disabling Nana, he attempts to rape Mayu, only to beaten back by the arrival of Bando, who is afterward furious to learn Lucy had been living nearby all along, known to Mayu, whom he trusted. Lucy takes over from Nyu and battles with Bando, with interference from Unknown Man ended by Lucy killing him. She then tries to kill Mayu, who is saved by Bando's sacrifice. Due to miscommunication, no one realizes Kurama is alive, though mentally unstable, and witnessed the battles.
Nana reveals her past to the grieving Mayu, and unwittingly reveals Lucy's existence to the innocent Nyu, who is horrified at the thought. Kouta gathers his family back to Maple House for dinner, while they await Nozomi's test results for entry to music school. Unknown to any of them, Chief Kakuzawa, working with the amoral scientist Nousou and with the aid of a professional Agent has readied an assault on Maple House, spearheaded by three Diclonius girls who are clones of the late Mariko.