Yoshiko is a diligent high school student who spends nearly all her free time trying to assist a hikikomori childhood friend and an eccentric, reclusive uncle. During a visit to her uncle's penthouse with two friends, Yoshiko spots a black, snow-like substance falling from the sky, though her friends see nothing. Shortly thereafter, a massive earthquake strikes the city, leaving Yoshiko, her friends, her uncle, and his dog trapped in an unfamiliar world... accompanied by a variety of strange individuals.