Few days before Little boy was dropped on Hiroshima the young boy Gen Nakaoka lives with his family in town where they struggle to make ends meet. Gens father Dakaichi, a critic of the war, shows up drunk to a mandatory combat drill and the family is branded as traitors by their neighbours. To restore their family honour Gens brother joins the Navy. When the bomb is dropped on August 6th, Gens father and siblings die, causing him to be left behind with his pregnant mother who then gives premature birth to his sister Tomoko due to shock. They struggle for survival, adopt the orphan Ryuta and Gen manages to save the girl Natsue, who is a burnt victim of the bomb, from suicide.