When their mother is killed in the firebombing of Tokyo near the end of World War II, teenage Seita and his little sister Setsuko are left on their own as their father is away, serving in the Japanese Imperial Navy. The two children initially stay with an aunt, but she has little affection for them and resents the time and money they require. The two children set up housekeeping in a cave by a stream, but their meager resources are quickly exhausted, and Seita is reduced to stealing to feed his sister. Despite his efforts, she succumbs to malnutrition. Seita painfully makes his way back to the devastated city where he quietly dies in a crowded railway station.