Monster Strike the Movie: Sora no Kanata

Thirteen years ago, a section of Tokyo suddenly broke away and began floating in the sky. The city was split into two: "Old Tokyo," the part suspended in the air, and "New Tokyo," the part remaining on the ground. For years, communication and travel between the two were impossible. One day, a young girl realizes Old Tokyo is about to crash back down. To save its people from disaster, she embarks on a dangerous journey from Old Tokyo to New Tokyo.