The episode begins with Kurama having saved Nana from falling from the bridge. Meanwhile, Lucy is shown to have Bando beaten again and leaves him behind.
In an inn, Yuka tells Mayu about Kouta's past. It involves with the fact that ever since he witnessed the death of father and sister by the hands of Lucy, he is traumatized and forgets about it. She reveals that she happens to be in love with Kouta.
Meanwhile, a scientist tells Kakuzawa about an army is murdered and the latter tells about Mariko could be useful in getting Lucy. The scientist puts down the phone and gets surprised to discover that Mariko happens to be Kurama's daughter.
Nana and Kurama are outside where Mariko is held and tells Nana that she is his real daughter. Lucy and Mariko sense each other. Inside, Mariko kills a soldier watching her and tells the scientist that she is ready to battle Lucy.
Upon seeing Mariko, Lucy tells her that she doesn't want anybody else involved and Mariko sends her vectors to her. Unfortunately, she has more vectors, forcing Lucy to run and hide. She manages to get Mariko off her wheelchair and tells her to run. Mariko laughs at this about killing her and punches Lucy continuously, getting her right horn broken. The scientist is watching and waiting to get Lucy. He has orders to kill Mariko after getting to Lucy.
Just then, Nana and Kurama are there. When Mariko calls for her father, Kurama pulls out a gun at her. Mariko says that she used to hope that when she was in that dark room that her mother and dad would come one day and pick her up and they would live happily together. She starts to cry and Kurama says that he killed many others but let her live and now feels guilty. Mariko asks why she had to live through that all those years. When Nana calls Kurama "papa", Mariko attacks her and asks Kurama that will he be sad if she dies. Kurama drops his gun and hugs Mariko. He says that he took everything from her and has been missing her ever since. He picks her up and says they will live together forever from now on. He says to Nana, "take care" and walks down the stairs with Mariko.
Nana and the scientist are watching the event as the latter is about to activate the explosives inside Mariko. Kurama tells Mariko that he and her mother love her very much and starts to cry. Mariko holds on to him tighter. The explosives activate and Kurama holds her tight. Shots of Mariko as a child growing up with her mother and father are shown and they explode.
When the scientist is about to kill Nana, Lucy kills him and tells her to live with Kouta as she is about to do something she couldn't do.
Director Kakuzawa happens to be revealed as a diclonius.
Kouta is sitting in the steps where he looks out. He sees Lucy with blood on her head and asks if she is hurt. Lucy replies that it is nothing serious.
Kouta puts together that the girl he saw in his childhood and Nyu happens to be Lucy all along. She tells him about her purpose to kill all humans and her memories with Kouta are the best. Lucy begins to cry and apologizes to Kouta for killing his father and sister. Just as she walks away, Kouta grabs her, telling her that even though he can't forgive her for the murder of his family, he still loves her and Nyu.
Lucy kisses him. Memories of their childhood are shown. Lucy says she wants to forget everything and be with him forever. She apologizes for bringing back some bad memory for him. Kouta says that she brought some good memory to him too and hugs her tight.
Nana is walking when she sees Lucy battle a giant army. The soldiers start shooting at her as her second horn brokes.
The credits has a figure appearing in the doorway of the inn.