The Mutou family enjoys a tranquil existence: Kouichirou is employed at a construction site, and his wife Mari is coming back from a trip abroad. Their daughter Ayumu has just completed her track practice, while their son Gou plays video games at home. Yet, their familiar world is turned upside down when a devastating earthquake hits the entire Japanese archipelago, instantly obliterating the country's landscape. As society disintegrates around them and their nation slowly sinks into the sea, the Mutou family must unite to endure the disaster. Navigating this near-apocalyptic environment, they fight not only for survival but also to grasp the hardship of dealing with loss.