The Place Promised in Our Early Days

In an alternate timeline, Japan was divided after World War II, with Hokkaido annexed by the Union and the southern islands under US sovereignty. A colossal and enigmatic tower was constructed in Hokkaido, visible from the northernmost prefecture of Honshu, Aomori, across the Tsugaru Strait. In 1996, three 9th-grade friends made a childhood promise to build an aircraft and unravel the tower's secrets, but their project was abandoned when one of them, Sayuri Sawatari, fell into a deep sleep and was transferred to Tokyo for treatment. Three years later, her friend Hiroki Fujisawa discovers that Sayuri has been in a coma ever since, and enlists the help of Takuya Shirakawa to revive her, unknowingly linking her unconsciousness to the mysteries of the tower and the world.