In 1958, thirteen years after the atomic bombing of Hiroshima, the city is slowly rebuilding. A young woman named Minami Hirano lives with her mother in a makeshift shanty town, carrying the invisible scars of the past. Having lost her father and sisters to the bomb, with her younger brother Asahi evacuated and living far away, Minami works as a clerk and attempts to find some sense of normalcy. She is courted by a kind colleague, Yutaka Uchikoshi, who gently encourages her to accept happiness. However, as Minami finally begins to open her heart, the first signs of radiation sickness appear on her body, forcing her to confront the legacy of the bomb that she can never truly escape. Decades later in 2004 Tokyo, Nanami Ishikawa, a young office lady, notices her recently retired father Asahi acting strangely, disappearing on unexplained trips. Concerned, she follows him one night, discovering that he is secretly traveling to Hiroshima. There, accompanied by her childhood friend Touko, Nanami trails her father as he visits graves and speaks with people from a past she knows nothing about. Through this journey, she slowly pieces together the story of her unknown aunt Minami, a woman who died young from the bomb's effects. Nanami begins to understand the heavy silence her family has carried for generations, the hidden grief of her father, and the way history continues to ripple through her own life and relationships.