At the end of World War II, Japan was split and a great tower was erected that reached the skies. For three friends, Hiroki, Takuya, and Sayuri, memories of their summer spent together would stay with them forever. During that precious time, the three promised to one day travel to the tower in the skies on the wings of a white plane -- to finally see its brilliance and the surrounding land of Ezo -- but when Sayuri suddenly disappeared from their lives, the promise that once was made was broken. Though time continues to pass, will the three ever meet again some day?