There is an estimated 70% or higher possibility that a magnitude 7.0 earthquake will occur in Tokyo in the next 30 years. In 2012, Mirai, a middle school freshman girl, goes to Tokyo's artificial Odaiba Island for a robot exhibition with her brother Yuuki at the start of summer vacation. A powerful tremor registering 8.0 on the Richter scale emanates from an ocean trench, the famed Tokyo Tower and Rainbow Bridge crumble and fall, and the landscape of Tokyo changes in seconds. With the help of a motorcycle delivery woman named Mari who they meet on Odaiba, Mirai and Yuuki strive to head back to their Setagaya home in western Tokyo.