The Place Promised in Our Early Days

Kumo no mukô, yakusoku no basho is a movie starring Hidetaka Yoshioka, Masato Hagiwara, and Yuka Nanri. In an alternate postwar timeline, Japan is divided into the Union-controlled North and the US-controlled South.
In a post-war alternative timeline, Japan is divided into the North, controlled by the Union, and the South, controlled by the United States. A mysterious high tower rises within the borders of the Union. Three high school students promise to cross the border with a self-built airplane and unravel the secret of the tower.