The real story
The tradition is called senbazuru. Cranes are a symbol of long life and good luck in Japan, and strings of a thousand are folded for weddings, for the sick, and for peace.
The cranes became known around the world through Sadako Sasaki, a girl from Hiroshima who fell ill years after the atomic bomb and folded cranes in hospital. Today children send strings of cranes to the Children's Peace Monument in Hiroshima, where her statue holds a giant crane above her head.