Starry Sky Volume 1 (Manga)

Tsukiko Yahisa is a college student majoring in astronomy. One day a single e-mail brings memories of the good old days at Seigatsu Academy. All those friends she made throughout the year, now scattered - she is wonders what happened to Yoh, Tsubasa, and Ryunosuke, and hopes they'd find each other and hang out like they used to once again.