Upon graduating from elementary school, Takaki Tono and his close friend Akari Shinohara drifted apart. Akari moved to Tochigi Prefecture due to her parents' jobs, while Takaki attended a junior high in Tokyo. The two kept in contact by writing letters, but despite the special feelings that existed between them, the only thing that persisted was time. When Takaki became aware that his family would move to Kagoshima, he decided to go see Akari since they would be too far apart to visit each other after he moved. However, when the day came, a severe snowstorm delayed Takaki's trip, and it would be hours before he reached Iwafune, where they promised to meet.

Takaki is now in the third year of senior high in Tanegashima, where the Tanegashima Space Center is located. Kanae Sumita, a classmate of Takaki, has special feelings for Takaki, but she does not have the courage to express her love to him. She later observes that Takaki is always staring off into the distance, as if searching for something far far away.

It is now 2008, and all three characters have gone their separate ways. Takaki is now a computer programmer in Tokyo, and Akari is preparing to get married. One day, Takaki goes out and sees the face of a familiar-looking woman at a railroad-crossing. Puzzled by the encounter, he tries to look back, but a train comes and cuts off his view.