战争之后，日本被分为南北两个部分。美军统治下的青森县，少年藤泽浩纪和白川拓也都喜欢同年级的同学泽度佐由理。他们的心中都有佐由理，还有那个东西——边境以北的津轻海峡，日本北海道联盟建立的高耸云端的“塔”。巨大而神秘的的塔，是三位少年少女的向往，他们约定，建造小型飞机，飞向 塔去一探究竟。 中学三年级佐由理转学到东京。两位少年放弃了制造飞机的打算。浩纪考进东京的高中，拓也继续留在青森的高中就学，彼此在各自的道路上越走越远。 但是，多年后，佐由理在医院中陷入沉睡！这突如其来的病症让三人再次聚在一起。沉睡的病症，与塔的力量有神秘的联系，而塔本身，似乎也成了日本南北开战的据点。 卷入战争与爱情的三人，到底是救佐由理，还是救世界！命运的解答，似乎就在云的那一端，他们曾经约定的地方。The story takes place in a alternate postwar period, in 1996, where Japan is divided. Hokkaido is ruled by the "Union" while Honshu and other southern islands are under US authority. A tall tower was built on Hokkaido, which could even be seen from Tokyo. In the summer of 1996, three middle-school students make a promise that they'll cross the border with a self-constructed plane and unravel the tower's secret, but their project was abandoned after the girl, Sayuri Sawatari, became mysteriously ill and transferred to Tokyo. Years later on the brink of another war Hiroki Fujisawa finds out that Sayuri had been in coma since then, and he asks Takuya Shirakawa to help him finding a way to wake her up.
