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, but Sora stays at home, refusing to go to school even as Haruka starts attending. Realizing that Haruka is growing more and more distant and slipping from her grasp, Sora goes to Haruka's room at night and appeals to Haruka as she removes her clothes...

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.

By now Sora is showing her hatred of Nao in the open, even in front of Ryohei and Nao herself. One afternoon Sora, attracted by the smell of curry cooking in the kitchen, catches Haruka and Nao making love in the living room. Sora throws Nao out of the house, warning her not to see Haruka ever again, since it is the second time she catches the two doing the "dirty deed."

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.

Haruka is trying to start a new life over with Nao, but Sora is always at the back of his mind, since, lately, she seems not to accept Nao, and that she seems to be teasing him. Haruka suggests a date with Nao, but cannot get to tell Sora about it, even disguising it as if he will be spending time with Ryouhei. During the date, though, Nao notices that Sora is never far from Haruka’s mind, him buying things for his sister rather than for her, and eventually spoiling their date. They plan to make croquette curry upon arriving home, but is canceled when Haruka finds Sora not feeling well in her room after having a bad dream. The next day Nao notices that Haruka tries to hide his date with her from Sora, but she just went along. One night, 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.

Kozue runs away in shock at the sight of the twins having Intercourse, 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 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.