history, the Soviet Union has taken control of the northern island of Japan and cut it off from the rest of the country. Just south across the strait, a boy named Hiroki is fascinated by the mysterious tower the Soviets have constructed on the unreachable island, and he and his friend Takuya decide to build a plane that will take them over to see it. As they work, a girl named Sayuri becomes a part of their lives and the promise to one day fly to the tower. But when she disappears without a trace, their promise I left unfulfilled--possibly forever.