A young girl named Suzu resides in the picturesque seaside town of Eba, located near Hiroshima. One day, she creates a heartfelt painting for her classmate, Tetsu, who gazes out at the sea and mourns the loss of his brother, a sailor who tragically drowned. In 1943, 18-year-old Suzu marries Shusaku, a military clerk whom she once befriended during her childhood, and moves in with his family in Kure, a prominent naval port city just 15 miles from Hiroshima. As she adapts to her new life, the shadow of the Pacific War begins to loom over the townspeople.
Situated on a hillside with a breathtaking view of the Combined Fleet in the harbor, Suzu's new home serves as a gathering place for her sister-in-law Keiko and niece Harumi, who visit occasionally. With the onset of food shortages, the government enforces rationing, and warnings about potential air raids from the United States unsettle the community. Suzu assumes the responsibilities of a housewife within the Tonarigumi, overseeing food distribution and participating in air raid drills and other wartime efforts.
In December 1944, Tetsu pays a visit to Suzu, now serving in the Imperial Navy. Aware that this may be their last encounter, Shusaku steps aside, giving them the chance to speak privately. Tetsu confesses his love, but Suzu reassures him that her heart belongs to her husband. The following spring, Shusaku is deployed, stationed 40 miles away in Otake City.
As 1945 unfolds, the United States commences air raids on the Japanese mainland, targeting Kure's bustling port. Suzu faces a series of devastating tragedies: she loses her brother Yōichi, sustains an injury that costs her right hand, and suffers the heart-wrenching loss of Harumi when a time-delayed bomb explodes nearby. Ultimately, Suzu, grappling with overwhelming sadness, yearns to return to her hometown but is stalled by a doctor's appointment. One fateful morning, she and Keiko witness a strange light followed by a violent tremor. With the radio down, they gaze toward Hiroshima City and are struck by a colossal cloud, soon learning about the catastrophic bomb that has devastated the city and claimed countless lives. For a period, Suzu is left in the dark regarding the fate of her beloved hometown.
Days later, the Emperor of Japan announces the war's end in a tragic radio address. Suzu struggles with the harsh reality of her losses, descending into despair as she becomes accustomed to the relentless fight to sustain her family. When the American forces occupy Kure, they bring food aid to the local residents. Suzu travels to her grandmother Ito's family home in rural Kusatsu, where she reunites with her sister Sumi, the sole survivor of her direct family. Sumi reveals the heartbreaking fate of their parents: their mother left for supplies and is presumed killed in the bomb's initial shock, while their father succumbed to an illness possibly linked to radiation. Unfortunately, Sumi herself is seriously ill from the same exposure.
Eventually, Shusaku returns to Suzu, and together, they find an orphaned girl whom they decide to adopt. With the support and love of her friends and family, Suzu gradually rekindles her spirit for life. As the film concludes, we see their adopted daughter thriving in the Hojo household, learning to sew clothes with Suzu's guidance in the rebuilding of post-war Japan.
