Imai Eisaku survived the Hiroshima atomic bomb, but he never told his two daughters about this. His eldest daughter, Yoshiko, works as a part-time tourist guide during the summer holidays and makes the acquaintance of a Hong Kong writer, Lee Hak-keung. She helps Lee collect information on the atomic bomb survivors and their descendants. The parents of Yoshiko's boyfriend, Kimura Makimune, ask Imai for Yoshiko's hand on behalf of their son. Imai then has to tell them that Yoshiko is the descendant of an atomic bomb survivor. That does not affect Kimura's love for Yoshiko. Yoshiko's sister, Kyoko, finds out by accident that Yoshiko is not her real sister, and that she herself is also a descendant of an atomic bomb survivor. When Yoshiko finds out about this, she leaves home. Yoshiko is in fact the daughter of Imai's best friend and his Chinese lover, Yu-fen. Ten years after the Second World War, Yu-fen went to Japan in search of her Japanese lover. She found Imai instead. They got married and gave birth to Kyoko. Yoshiko finds herself with leukaemia and decides to give the rest of her life to the anti-nuclear peace movement, to stop the nuclear-armament race of the world's super powers and to raise the world's awareness of the fate of the atomic bomb survivors