1945, Japan. Gen Nakaoka is a spirited six-year-old boy who lives with his poor yet loving family in wartime Hiroshima. As the second World War rages on, Gen's father Daikichi stands among the few outspoken who are opposed to the emperor and stand for the innocent civilians bearing the brunt of the war. However, in a society with nothing but feverous support for their nation, Gen and his family are ostracized as traitors. Unbeknownst to them, a terrible fate awaits the people of Hiroshima...

One quiet morning, the US forces drop an atomic bomb on Hiroshima. In an instant, the city is completely destroyed, leaving thousands dead and many more exposed to radiation. Though Gen manages to survive the blast, he finds his life irreversibly changed. Regrouping with what's left of his family, Gen must now grapple with starvation, destitution, and an unsympathetic public who see survivors as little more than disease-ridden beggars.

Based on author Keiji Nakazawa's real-life experiences, Hadashi no Gen follows Gen and his fellow survivors in their struggle to survive in post-war Hiroshima. Gen resolves to soldier on with unwavering determination, while never forgiving those who caused the atrocity, never forgetting the pain of the bomb, and never letting his spirit be broken by the tragedy.