An apocalyptic look at the possibility of an earthquake of magnitude 7 or greater striking the Tokyo area. Mirai, a middle school freshman girl who goes to Tokyo's artificial Odaiba Island for a robot exhibition with her brother Yutaka at the start of summer vacation. A powerful tremor emanates from an ocean trench, the famed Tokyo Tower and Rainbow Bridge crumble and fall, and the landscape of Tokyo changes in an instant. With the help of a motorcycle delivery woman named Mari who they meet on Odaiba, Mirai and Yutaka strive to head back to their Setagaya home in western Tokyo.