Susumu's Story is set in the city of Hiroshima during the Second World War. Susumu has a very good friend, Kiyoko. The children's fathers are sent to war. Susumu dreams of becoming a pilot and joining his father in battle.
Kiyoko misses her father and knows that war is not a game.

At school, they work to build a garden, planning to plant a young cherry tree, a symbol of their own hopeful future.

On Kiyoko's fourteenth birthday, she hears at last that her father is coming home. As Susumu leaves the city to go to the country with his mother, a bomb falls on Hiroshima.