Middle school student Mirai Onozawa is dissatisfied with her family circumstances and, in a moment of frustration, wishes to tear everything apart. Unfortunately, these destructive thoughts seem to come true in the form of a magnitude 8.0 earthquake just a few moments later.

When summer vacation begins, Mirai reluctantly takes her younger brother Yuuki to Odaiba, where a robot exhibition that he wanted to go to is being held. However, while they are in the exhibition center, the fury of a major earthquake shakes the Kanto region; helpless, both kids witness the devastating power of this natural disaster as it brings the city to its knees.

In its aftermath, they stumble upon Mari Kusakabe, a motorcyclist and single mother who decides to help the young siblings. Aiming to return to their homes and reunite with their families, the group sets off on a long and hard journey through the decimated city.