Sadako's family was forever affected by the radioactive fallout from the atomic bomb that was dropped on Hiroshima towards the end of World War II. Sadako was just two years old at the time. Although the blast blew her out the window, she survived the initial explosion with barely an injury. However, about ten years later, Sadako fell ill to the "Atomic Bomb Disease." This was the cancer that so many people, particularly children, who were near the atomic bomb blast later developed years afterward.
Sadako's pain as she suffered through this terminal disease also caused great suffering for her family who witnessed it. Sadako does what she can to keep her parents from worrying, but this is impossible to do, as other children in the hospital's cancer ward die at an alarming rate. After eight months of intensive and painful treatment and her dedicated efforts to make one thousand origami cranes, Sadako succumbs to the cancer and dies.
The death of Sadako left a hole in the family that never truly healed. Yet, the young girl's spirit of perseverance and hope inspired them to share her story with the world. They collaborated with the writing and publication of Sadako and the Thousand Paper Cranes and her brother, Masahiro, wrote a biography of Sadako as well.