All of Sadako’s friends and family start saving paper for her to use to make the good luck origami cranes. Chizuko brings Sadako paper from school, her father saves every scrap he can from his barbershop, and Nurse Yasunaga gives Sadako wrappers from packages of medicine. Masahiro hangs every one of Sadako’s birds from the ceiling for her. She folds over three hundred as the months pass by.
As Sadako takes comfort in the making of the cranes, her friends, family, and caretakers, too, become invested in her journey and inspired to help her as she perseveres in search of hope in the face of her debilitating illness. Sadako’s optimism, hope, and perseverance are an inspiration to others during her life, not just after her death.
As the leukemia begins to sap Sadako’s energy, she experiences throbbing headaches, pain in her bones and her joints, and suffers more and more dizzy spells. One day, when Sadako is feeling especially tired, Nurse Yasunaga wheels her outside to get some fresh air and see the sunshine. Out on the porch, Sadako sees a boy, whose name is Kenji. He is nine years old and small for his age. Sadako introduces herself, and soon the two are talking like old friends. Kenji has been in the hospital for a long time but has very few visitors—his parents are dead. Kenji insists that it doesn’t matter that he has no visitors—he will be dead soon, he says, of leukemia contracted from the atom bomb.
Sadako has support and solidarity from those outside of the hospital, but very few friends inside the hospital. When she meets Kenji, she sees someone whose struggle very closely mirrors her own. Whereas Sadako, however, has chosen to subscribe to hope in the face of her illness, Kenji seems resigned to being sick. He has come from a much more difficult background and does not have the same support system Sadako does, and his will to persevere, it is implied, is compromised by his lack of friends and family.
Sadako tells Kenji that he can’t possibly have leukemia—he wasn’t even born when the atom bomb was dropped. Kenji explains that the radiation poison got into his mother’s body and was passed onto him. Sadako doesn’t know what to say to comfort Kenji, but soon thinks of the cranes, and tells Kenji that he can start folding with her if he likes. Kenji insists that it is too late, though, and even the gods cannot help him now. Nurse Yasunaga comes out and scolds Kenji for thinking so fatalistically, but Kenji tells her that he can read his blood count on his charts, and knows he is getting worse every day. Nurse Yasunaga wheels Kenji back inside.
Sadako, seeing Kenji’s low spirits and hearing the sad story of his illness and isolation, volunteers to help him and bring him into her crane-building project. Sadako has seen how the cranes have helped not just her but everyone around her to come together, and hopes that the cranes will have this effect on Kenji, too. However, the somber Kenji is unable to see past the suffering inflicted by his illness in order to see the point of fighting for his future.
Back in her room, Sadako tries to imagine what it would be like to be sick and have no family. She thinks of how brave Kenji is, and makes a big crane for him out of her prettiest paper. She brings it across the hall to him, and then begins folding more birds for her own flock, reaching four hundred cranes—a big milestone.
Kenji’s fatalism doesn’t bring Sadako down at all—rather, it inspires her to build even more cranes for herself and to show Kenji some support and solidarity, even though he does not have the same hope and drive that she herself does.
Late one night, Nurse Yasunaga comes into Sadako’s room to inform her that Kenji has died. Sadako cries, but Nurse Yasunaga comforts Sadako by assuring her that Kenji has shed his tired body and now his spirit is free. Sadako asks Nurse Yasunaga if she herself will die next, but Nurse Yasunaga assures Sadako that she won’t. Nurse Yasunaga urges Sadako to build one more paper crane before bed, and promises her that once she makes it to one thousand cranes she will live to be an old woman. Sadako folds some more cranes, each time wishing that Nurse Yasunaga’s prediction would come true.
Kenji’s death marks a turning point for Sadako. Up until this point, she has seen her illness as something she must overcome. Even though she was in constant pain, she could not understand why Kenji could not see things in the optimistic way that she herself saw them. But now Sadako must face the fact that leukemia might not, in fact, be beatable—that Kenji’s pessimism might actually be realism, and her own optimism might be unfounded. And she begins to think differently about death. She has until now seen freedom as only possibly by beating death. But now, as Nurse Yasunaga explains that Kenji’s illness was so terrible that death was the only thing that would bring him freedom and peace, Sadako understands that there are many different kinds of freedom. She continues folding cranes, though, and remains steadfast in her plans to make a wish for her own recovery.