1Primera Flor
Koshiro se está recuperando de la ruptura con su novia. De camino al trabajo en el tren, se encuentra por primera vez con Nanoka mientras devuelve una etiqueta con su nombre que se le cayó cuando intentaba salir del tren. Después de regresar a su casa del trabajo, se entera por su padre de que su hermana, cuyo rostro ya no puede recordar, se mudará a su casa para facilitar el viaje a la escuela.
2Aprensión De La Primavera
Koshiro se siente incómodo con la presencia cariñosa de Nanoka mientras lucha con sus sentimientos por ella. Llega a su límite cuando ella llega a su oficina para visitarlo, gritándole y diciéndole que nunca más lo visite y que deje de llamarlo Gran Hermano.
3Brisa Suave
Incapaz de dormir, ocupado con pensamientos sobre Nanoka, Koshiro recuerda cómo en su infancia lo ayudaba a dormir en esas noches de insomnio. Mientras tanto en la escuela, la amiga de Nanoka se enamora de un chico solo para descubrir que es el novio de Tamaki.
4Lluvia Vespertina
Mientras va al cine con su hermana, Koshiro es descubierto por su exnovia. Temeroso de que ella haya pensado equivocadamente que él estaba buscando chicas de secundaria, queda con ella para cenar y explicarle.
5Trueno Distante
Koshiro se sorprende al descubrir que Nanoka ha vaciado el cubo de basura de su habitación que contenía los pañuelos de su culpa. Le grita por invadir su privacidad. Esa noche, vuelve de beber y deja caer y rompe su cuenco de arroz cuando ella lo sorprende contemplándolo. Al día siguiente, cuando su padre llama a Koshiro al trabajo y le pide que se reúna con Nanoka en la estación con un paraguas, descubre que es el cumpleaños de Nanoka.
6Pensamiento De Otoño
Nanoka descubre que en la escuela se ha ganado la reputación de tener complejo de hermano. Después de trabajar hasta tarde en el festival escolar que se avecina, un compañero de la escuela la acompaña a casa. Koshiro se encuentra con ellos y le grita por ser tan imprudente con los chicos, ella protesta. Al día siguiente, ella lo evita yéndose temprano y la empujan y manosean en el tren.
7First Thought
Nanoka receives a love letter at school. She doesn't know what to do about it. She asks Koshiro what she should do about the love letter and he indifferently says she should make up her own mind and not consult him. She meets with her admirer and turns down his advances and then is disappointed when he doesn't seem to care. Koshiro regrets his prior indifference and tells Nanoka that if she wants advice about anything, she can ask him. She is impressed by his concern about her and says "I love you".
8Frozen Dew
Koshiro remembers the birth of his sister and their life together before their parent's divorce. Although they were too far apart in age to understand each other, they felt a vague sense of affection. In the present, Koshiro goes to see his mother for the first time in many years. She tells him how much Nanoka looked up to her big brother and tells him to be a good big brother to her. On the ride back, he remembers an incident when baby Nanoka gave him a glass of mud and he ended up keeping it because it made her so happy. He resolves to be a good big brother to her.
9Snow Flakes in the Wind
Koshiro contemplates moving out to resolve his situation while Nanoka plans to make him a sweater for Christmas.
10Wintry moon
Koshiro mentions to Kaname that he is thinking of moving out. She pushes him into doing it right away. Nanoka doesn't want to go home, so she arranges to stay overnight at her friend's house where she watches two normal sisters bicker and laugh. Koshiro and Nanoka make up on the phone. Koshiro announces to the family that he's moving out. Nanoka comes to his room and asks if they can sleep together. He agrees on the condition that they not meet again. She wakes up in the morning alone in an empty room and cries.
11Lingering Winter
A month and a half after Koshiro has moved out, both the siblings are still thinking of each other, but keeping their promise not to see each other again. Nanoka sometimes walks by his new apartment or place of work, but avoids meeting him. Kaname has taken to sleeping over at Koshiro's place because "it's closer to work". One day when they are going to his place, they see Nanoka outside. He pushes Kaname away to hide from Nanoka, and Kaname guesses why he left home and is hiding from Nanoka. She confronts him, accuses him of perversion, and walks away. He stays home from work. When he opens the door to go to the store, Nanoka is standing there.
12Spring Thunder
Nanoka breaks their promise and comes to Koshiro's apartment to see him. She offers to make him a meal, but his refrigerator is empty so he goes out to pick up some things. In the meantime, Kaname drops in and is shocked to find Nanoka there. She tries to make Nanoka go home by telling her that she is going out with Koshiro. But Nanoka refuses, saying that her feelings for her brother are greater and she insists that Kaname leave instead. Kaname encounters Koshiro on his way home and tries to talk sense into him, but he won't listen. Kaname says that she will not interfere any more. The siblings decide that they really do love each other and want to be together no matter what. They spend the night together as lovers.
13Heat Haze
Nanoka and Koshiro visit Mama together. After, sitting by the sea, Nanoka asks Koshiro if they should commit lover's suicide. He cries and says he doesn't know. She says that she is fine either way as long as she is with him. Koshiro quits his job. On his way out he meets Kaname, who wishes him well. Koshiro stands outside his father's house and says "Excuse me". The couple frolic in the playground to the disapproving stares of the local matrons. Then at night they sneak into the amusement park where they met. They sit on the ferris wheel and try to move it by prayer. It moves a bit. They carve their names on a tree and promise to go back there every year. When Nanoka has walked off to go home, Koshiro says "I love you".