Gen Nakaoka, a Japanese boy in wartime Hiroshima, survives the atomic bombing at age six, shielded by a crumbling wall as the blast claims his father, siblings, and countless others. His family—pacifist father Daikichi, mother Kimie, and siblings—endures public scorn for Daikichi’s anti-war views, branded traitors in a nation gripped by conflict. Amid the bombing’s aftermath, Gen aids his pregnant mother in delivering his sister Tomoko amidst rubble and ruin, revealing early resilience and responsibility.

Struggling to survive, Gen scavenges for food in a shattered city, confronting radiation-sickened survivors and societal collapse. He adopts Ryuta, an orphan bearing a haunting resemblance to his late brother Shinji, forging a bond anchored in shared trauma. Tragedy compounds as Tomoko succumbs to starvation and Kimie dies from radiation poisoning, leaving Gen to face loss and desolation alone.

Interactions with a scarred postwar world mold Gen’s resolve: Mr. Pak, a compassionate Korean immigrant, provides aid; Katsuko, a fellow orphan, becomes his protege. These bonds fuel his emerging leadership and empathy, driving him to champion hope and defiance against oppression, inspired by his father’s metaphor of wheat enduring harsh soil. Postwar hardships—yakuza exploitation, encounters with American occupiers—deepen his opposition to militarism and nuclear arms.

Gen’s ingenuity surfaces in makeshift shelters built from debris and calculated risks like stealing medicine for the ill. Despite hair loss and looming fears of radiation sickness, he persists, honoring his family’s memory through relentless advocacy for peace. His journey—from a child shielded by a wall to a beacon of endurance—mirrors the series’ exploration of resilience against systemic failure and the human capacity to endure catastrophe.