Tomoko, a sixth-grade elementary school student in Hiroshima, undertakes a summer school project titled "My Adventure." This project prompts her solo visit to the Hiroshima Peace Memorial Park and Museum. Confronting exhibits detailing the atomic bombing plunges her into profound distress and fear. She specifically worries about vanishing like the victims and questions if this terror signifies cowardice.

Near the Children's Peace Monument, Tomoko folds a paper crane from a candy wrapper. This simple act triggers a transformative encounter with Sadako Sasaki, a girl who experienced the bombing at age two and later succumbed to leukemia. Sadako guides Tomoko onto an unexpected journey, riding a crane that traverses the globe.

Their flight exposes Tomoko to worldwide movements for peace and activism against nuclear weapons. Through her experiences with Sadako and the insights gained during their travels, Tomoko undergoes a fundamental transformation. Her initial shock and fear evolve into a deeper understanding of war's consequences and a personal commitment to peace advocacy. Her story concludes as she internalizes these lessons, recognizing the critical importance of collective pledges for peace to prevent future tragedies.