Miki's parents call her down for tea and cake. They say that they have something to tell her. They are thinking of getting a divorce. And they are happy about it! They tell her about meeting the Matsuura's on their Hawaiian vacation and that her father fell for Chiyako Matsuura and her mother fell for Youji Matsuura. The are going to get divorce and remarry the other's partner! They reassure Miki that they still love each other, it's just more of a sibling type of love. Miki can't believe what they are saying and tells them to change things back the way they were. Miki's mother, Rumi, asks her to forgive them.
The next day at school, Miki tells all of this to her best friend, Akizuki Meiko. Meiko tells her that she thinks it will be cool to have 2 sets of parents. Miki says that if it were her, Meiko would feel differently. Meiko tells her that she's wrong. Her parents don't love each other anymore and the only reason they don't divorce is for financial reasons. Meiko wishes they would separate soon. She then says that she never wants to marry. Miki figures that is the reason she never dates even though she is so popular. Meiko claims that is not the case, she just hasn't met anyone her type.
Suou Ginta, Miki's friend and tennis partner, shows up and wonders if she is going to practice. She tells him that she can't make it and Meiko wonders why. Miki whispers to her that she is meeting the Matsuura's for dinner that night. She hopes that if she can get them together, she can talk some common sense into them.
At dinner, Miki meets the Matsuura's. At first she thinks that they look like normal people but when she asks, they tell her that they plan on going through with the partner swap. She decides they are not normal at all. Miki then learns that the Matsuura's also have a child, Yuu-kun. He is Miki's age. Miki plans on getting him to help her gang up on the parents. Yuu walks in and he is drop dead gorgeous. Miki feels lucky to meet such a handsome guy. Then she comes to her senses and gets her resolve back.
Miki confronts the parents and tells them that she is opposed to the whole plan. She wonders what their relatives would say. Rumi tells her that they already told everyone and that it is ok with them. Jin, Miki's father, tells Youji that they have been doing whatever they wanted since they were children. Youji tells him that he has too. Rumi tells Miki she is too young to be so hard-hearted. Miki says wonders what they think about her's and Yuu's feelings. Yuu tells her that he doesn't care. She can't believe it. He tells her that as long as the people involved are happy, who cares what other people think. She figures out that he is strange.
Miki starts crying and says that it will be hard being separated from both her mother and father. They tell her that it has all been worked out. They will rent a bigger house and all six of them will live together. The parent-child relationships will stay the same. Miki is very confused. Jin asks her if she is still opposed. She starts to tell them that she is but then she looks at them again. After fighting with herself, she tells them that she understands. The parents celebrate.
In the next scene, moving vans are pulling away from a large house. They are all moving in together. Yuu asks Miki to go shopping. He picks on her.
At school the next day, Meiko asks Miki how her new life is going. Miki shushes her. She doesn't want anyone else to know. Miki says that school is the only way she can escape. Just then, Yuu bangs her on the head with his briefcase. She asks what he is doing there. He says that he transferred schools so her strange family is still going to be near her.
Ginta comes up to Meiko and asks who the guy is with Miki. He asks if he is a friend of Miki's. Meiko says that they look more like siblings to her. Ginta is confused. Ginta calls out to Miki and they go practice tennis. Meiko introduces herself to Yuu. Yuu asks if Ginta is Miki's boyfriend. Meiko tells him no but they have a good relationship. Yuu asks if they are ready to admit how they feel. Meiko tells him that Miki told Ginta how she felt the last year of middle school but that Ginta dumped her right away.
Later, Miki is showing Yuu around. They run into Namura-sensei (Na-chan to his students) and Miki points out that he is a good teacher and also the advisor for the tennis club. Miki asks Yuu which club he is going to join. He tells her none of them. Miki asks why and he tells her that he doesn't want any restrictions on his time. He then looks out the window and asks about the building across from them. She tells him that it is the library but not too many people go there since it only has old books in it. He then tells her that he is cutting 5th period but he will be back in time for P.E. She is stunned.
In P.E. class, Miki notices that Yuu is really great at sports. She is so busy concentrating on him that she doesn't see the ball coming straight at her. She is knocked unconscious.
Miki wakes up in the school infirmary. Meiko goes to get her school bag when Yuu enters the room. Miki thinks that he is going to do something insulting again so she pretends to still be asleep. He comes in and looks at her. He then leans over and kisses her. When she doesn't move, he leaves.
Miki sits up, grabs her mouth, and wonders what he is up to.