Mother Shizuko (Shibuya) waits impatiently for a bone marrow donor for her daughter Rika, who has leukemia. However, no donor was found, and Rika's condition worsened day by day. "The probability of finding a donor is 1 in 20,000 to 30,000. But if you are a sibling, the probability is 1 in 4." The doctor's words pierce Shizuko's heart... her son, Fumio, whom she lost 18 years ago. If so, she might be able to save Rika.