The Mutou family lives in Japan, where Kouichirou works at a construction site and Mari is a returning traveler. Ayumu has just finished track practice, while Gou is at home playing video games. A massive earthquake suddenly devastates the Japanese archipelago, destroying the country's coastlines. The family is forced to cope with the disaster's aftermath, as Japan sinks into the ocean, and learn to deal with their personal losses amidst the chaos.