As Chief Kakuzawa speaks to Arakawa about his scheme to overthrow humans with Diclonii in as little as a year, Kurama confirms the truth to both Nana and Mariko that he is Mariko's true father, and that he did indeed try to kill her when she was born. He begins to reflect on his past and how it led to all this, starting with his recruitment into the National Institute On Human Evolution by his old associate, Yu Kakuzawa. It is a choice the newly married Kurama comes to regret quickly and thinks poorly of the treatment given the young Diclonius girls who are their test subjects. The origin of these girls remains a mystery at that time, with Kurama also concerned for his sick wife, Hiromi, who tries in vain to become pregnant and carry a child to term. An encounter with one of these escaped girls unknowingly infects him with the virus that causes the mutation. When Kurama begins to willingly (though reluctantly) euthanize the infant girls born this way, including the daughter of his soon-to-be resigned assistant, Oomori. Soon after, he receives a great shock when his and Hiromi's daughter, Mariko, is born a Diclonius. The dying Hiromi, who can never have children again, in any event, pleads with her husband to let their daughter live. She then collapses to the ground and dies in his arms. Kurama, who now knows the way the mutation pushes forward, falls even deeper under the sway of the Kakuzawas as he makes the deals necessary to keep Mariko alive.
Kurama explains that all Diclonii, including Nana, have an inborn desire to kill humans and replace them by infecting males. He then tells Mariko that he is sorry, but he must cease his hypocrisy and end her life, just like he ended the lives of so many other girls. Mariko's offense and anger by the news, and Kurama embracing Nana triggers the return of her vectors, at which point she attacks Isobe, who holds the remote control for her internalized bombs.