Cranes are known as auspicious birds in Japan. 1000 of paper cranes are linked and given to people who are injured or sick as a prayer for recovery.
The origin of it is one of Hiroshima atomic bomb victims. She had an acute leukemia 10 years later from the explosion. She believed that if she made a thousand of paper cranes, she would survive, and the believing kept her making paper cranes. She ended up passing away 9 month later.
A string of thousand paper cranes is made for praying a recovery, but it’s also made as a symbol of an antinuclear movement, a peace.