Based on Makoto Shinkai's film, Byousoku 5 Centimeter follows the life of Tohno Takaki, Shinozaki Akari, and Sumida Kanae. The manga follows the three and their different view points as they chronicle their way through life.

From Dazzling Scans:

Kazusa, a young high-school girl, is killed instantly when a car crashes into her as she was crossing the street. As a ghost, she watches her friends' reactions to her death—keeping a close eye on Miharu, the boy she was in love with before she died. However, she discovers that he was in love with another girl Okabe Ranko... but can Okabe see Kazusa's ghost when no one else can?