Shortly after the Tokyo Olympics in 2020, a major earthquake hits Japan. Amidst the chaos, siblings Ayumu and Gou of the Mutou household, begin to escape the city with their family of four. The sinking Japanese archipelagos, however, relentlessly pursue the family.

Plunged into extreme conditions, life and death, and the choice of meeting and parting—in the face of dreadful reality, the Mutou siblings believe in the future and acquire the strength to survive with utmost effort.