When the Kasugano twins last visited the area, their departure was particularly painful for Nao, who had grown quite close to Haruka, to the point of having sex with him on one occasion, about which she feels guilty after she saw Haru's reaction after they had sex. Upon their return, she attempts to rekindle their former close relationship. Sora, her former best friend harbors, great resentment towards her because Sora thinks that she will steal Haruka away after saw the pair having sex when they were younger in a summer.
In the attempt to restore her former relationship with Haru, she explained that she was troubled by her parents constant arguement going in the house and wants to release her tension by finding Haru to have sex. She also clarifies that she cannot just find anybody to have that kind of relationship with.
Not long after reconcilating with Haru, she questioned Haru on whether he loved her or not when he tries to shake Sora's masturbation scene off his mind by bringing her into a hotel room to make love and he replies that he doesn't know.
One afternoon, when Kozue and Nao decide to visit the Kasugano residence, they catch the twins in the middle of making love. Kozue runs away in shock at the sight of the twins making love, while Nao calmly left the scene, but Sora wouldn't even care. Haruka thinks of ditching school, but she tells him to think little of it. Kozue tells him the next day that she'll never talk to him again, while Nao effectively ends her relationship with him after accepting his apology.
She got to know Sora had saw that they had sex when they were younger in a summer day and that "now they are even." Days later Haruka and Sora leave the place to live together overseas in the city where an artisan who had connection with their parents lived, hoping to find happiness elsewhere. Though Kozue disagrees, Nao believes they will do just fine.
After the sudden death of their parents, Haruka and his twin sister, Sora move to the house formerly inhabited by their late grandfather, in a small village they often visited as children. There, Haruka encounters several of the residents, some of whom are old friends like Nao, but Sora stays at home, refusing to go to school even as Haruka starts attending
This episode replays the event where Sora asks Haru to take her measurements so she can have a uniform made. The next day Nao comes over to bring Haruka some mosquito repellent, since Sora is scared of mosquitoes, and then leaves almost immediately. The next day Ryouhei invites Haruka to the school rooftop to take a peek at the girls cleaning the pool. Haruka warns Ryouhei, though, not to peek at Nao, and leaves. Much later Ryouhei tells Nao that Haruka, “the prince she has been waiting for,” has a crush on her; but she thinks he does not like her. The truth is that something happened between the two many summers ago: Nao, trying to escape the noise of her arguing parents, ran to Haruka's house. At that time Haruka was sleeping at their veranda, and was surprised to see Nao on top of him with her clothes undone. Until now Nao feels guilty for what she did. However, Ryouhei, even Akira and Kazuha, is into the act of bringing Haruka and Nao together. They did so by making the two meet at school pool on a Sunday. When they were changing after the swimming lesson, Haruka rushes into the girls' locker room when Nao was scared by a black cat inside a box. The school supervisor hears their chatter, but the two were able to hide inside a box before he catches them. Thinking it was just the cat, he leaves. There, Nao gets to know that Haruka does not hate her, only that he was just surprised at the events of that summer day, dispelling her assumptions. Meanwhile, Sora shows her hatred of Nao, whom she thinks is the reason why Haruka has been preoccupied the past couple of days, at home on her laptop.
Our episode begins with Sora waiting for Haruka at the door. She then hears Haruka telling Nao that he will tell Sora about them being in love. Sora surprises Haruka has he enters through the door. She tells him that she is hungry and he says he will make some curry for her. But Haru seemed to forget to go grocery shopping so instead they have some tuna and rice. Haruka tries to tell Sora about his relationship with Nao but, Sora says she does not want to talk since she heard the whole thing earlier. Sora wakes up early for school so she could avoid having any sort of contact with Haruka. During lunch, Nao asks Haruka to tell Sora to join them. As Nao is talking to Ryouhei, they overhear the conversation between Haruka and Sora. Sora was telling Haruka that she does not want to join them and have anything to do with Nao. Sora then notices that Nao heard her but just walks away without saying anything. Sora's temper is starting to reach it's limit by now.
Sora sends Haru a text message saying that she is leaving first and that she will be late. After school, Haru and Nao are at the grocery story and decide to pick up some ingredients to make some curry for Sora. As they arrive at home, they both notice that Sora's shoes are not there so they figured she hasn't come home yet. As they wait for the curry to finish cooking, Haru and Nao being to look at some photo albums. The both then start to kiss when Haruka tells her that he wants to fill the rest of the album with more memories of her. The scene then shifts to Sora sleeping in her room as she is awaken from the smell of the curry cooking in the kitchen. She then makes her way out of the kitchen she hears a noise coming from the other room.
As Sora peeks through the door, she sees Nao and Haruka having sex. Sora then opens the door and kicks Nao out of the house. Sora knows that this isn't the first time she has seen them having sex. She also saw them when they were kids. She warns Nao to stay away from Haruka and to never show her face in front of him again. Sora then runs into the kitchen and throws away all the curry that Haruka and Nao made for her. She says that she only wants Haruka's cooking and not Nao's.
The following morning, Nao tries to avoid seeing Haruka and Sora. Haruka finally meets up with her when she was hiding around the corner of her classroom. But she runs away because she is still unable to deal with the situation. After school, Haruka meets up with Nao at the grocery store. He tells her that he intends to make things right and to keep making her smile. The next morning, Nao comes over to pick them up for school. Sora seems to have calmed down a bit but continues to distance herself from them. It's a hot day so the whole gang decide to meet up at the beach. Thanks to Ryouhei, everyone now knows about Haruka and Nao's relationship
Sora decides to follow everyone at the beach, but at the moment she got off the bus, news that a young man was rescued from drowning unconscious. As Sora looks over, she finds out that the boy in question is Haruka. However, Nao acted quickly and performed mouth-to-mouth resuscitation. With that event, Sora becomes even more insecure, eventually telling Haruka not to leave home and tells all sorts of excuses just to make him stay. One day, Sora made Haruka choose between her and Nao, but he just shrugs it off and proceeds to school with Nao as if nothing is wrong. That afternoon Haruka finds Sora missing after receiving a text from her saying "Let's leave here." Akira, Kazuha, and Ryouhei joins Nao and Haruka in search of her, until, amidst the rain, Nao finds Sora at the bus stop. Refusing to go with Nao, Sora runs out of the bus stop, angrily telling her that she is the reason why Haruka has changed. Suddenly, a bolt of lightning strikes the bus stop and burst into flames. Sora then remembers she forgot her stuffed bunny inside. Nao rushes in to retrieve the only memento Sora has of her mother, causing her to be nearly trapped inside. After receiving the rescued item, Sora reveals to Nao her insecurities with her, that she is afraid Haruka would leave her alone. The next night, Sora joins everyone during the Summer Festival at the shrine. This time, Sora is more receptive of Nao.
Haruka was having a dream about when they were kids and Sora was discharged from the hospital. He is then awaken from it when Sora came over and kissed him. Looks like Haru has some deep feelings for his little sister.
The next day, Nao and Haru agreed to a date on Sunday. But, Haru forgot that he agreed to go with Sora to shop on the same day. Haru then lied to Sora and told her that he had plans with Ryouhei even though he was going on a date with Nao. Sora told Haru to cancel his plans but Haru said he would go with Ryouhei instead. This did not go well... While on his date, all Haruka could think about was Sora. Nao even tried to grab Haruka's hand but instead he ran off to buy something that Sora might like. The two then decide to make some curry for them and Sora.
When they arrive, Haru finds Sora crying in bed. Haru then tells Nao that Sora isn't feeling well and that they have to end their night together. Sora then tells Haru that the reason she was crying wasn't because she was sick but because she had a dream about losing Haru. The next day, Sora finds out that Haru went out with Nao and not Ryouhei when Haruka tries to hide it from her. Nao got the impression that Sora didn't want her around. I'm pretty sure she was spot on. One night, Haru went to the kitchen for a glass of water. He then hears his name coming from Sora's room... Haruka catches Sora masturbating in her room while mentioning his name, much to his dismay—she is enamored with him ever since that one summer day in their childhood when Haruka kissed Sora while playing.
Haruka takes Nao out on a date again, but he cannot shake the sight of Sora masturbating that night off from his mind. Eventually Haruka hits his limit and in an attempt to get rid of those thoughts, he starts taking Nao to a hotel and tries to make love with her in a forced way, but she rejects his act and asks if he really loves her. Haruka is unable to answer and returns home. Soon after, Sora gets a fever and Haruka stays home to take care of her. That evening, Sora, with her fever subsided, confesses her feelings to Haruka and the two make love, beginning a relationship. This did not go unnoticed, as everyone, especially Kozue and Nao, begins to see the twins spend more and more time with each other. One afternoon, when Kozue and Nao decide to visit the Kasugano residence, they catch the twins in the middle of making love.
Kozue runs away in shock at the sight of the twins making love, while Nao calmly left the scene, but Sora wouldn't even care. Haruka thinks of ditching school, but she tells him to think little of it. Kozue tells him the next day that she'll never talk to him again, while Nao effectively ends her relationship with him after accepting his apology. That night Haruka fights with Sora when he tells her that they stop doing it, even inadvertently hitting her. Things get complicated when they find out that their parents left no money for the two, and in order to survive they have to be taken under custody of their relatives, but this means them living apart. That afternoon Haruka awakens to find Sora missing and her room in a mess. He goes looking for her after receiving a text from Sora which sounds like a suicide note. Nao even helps him in looking for her everywhere, mentioning to him about her confrontation with Sora, saying she has seen the two making love that summer day, and that "now they are even." Haruka then remembered the lake Akira mentioned the other day. Haruka finds Sora, and his attempt to stop her from going deeper in to the lake nearly ends in them drowning. Days later the two leave the place to live together overseas in the city where an artisan who had connection with their parents lived, hoping to find happiness elsewhere.