After their promise to visit Hokkaido, Sayuri mysteriously disappears during the summer. Three years pass and Takuya and Hiroki have stopped working on the plane, taken different paths after the grief they suffered at Sayuri's disappearance. Although only in high school, the brilliant Takuya is working as a physicist at an Alliance scientific facility they know that the Hokkaido Tower, which began operating in 1996, replaces matter around it with matter from other universes, but they do not yet know why it does this for only a 2-km radius. And as things progress, more mysteries start to surfa…