Tell me more! (The Japan Forum) Putting up koinobori, or streamers in the shape of carp, is a spring tradition in Japan. Colorful cloth carps flying against the blue sky can be seen across Japan from the end of April until May 5, Children's Day. The tradition is said to have begun in the Edo period (1603-1868) based on a Chinese legend about a strong, brave carp swimming upstream and becoming a ..