May 5th is a national holiday in Japan to respect children’s personality and wish their happiness. This day is called Children’s day in English and Kodomo-no-hi in Japanese.
People celebrate Kodono-no-hi by putting up carp streamers which is called Koi-nobori in Japanese (Koi means carp in English). Koi-nobori is made of papers or clothes, and shaped like carps.
Kodomo-no-hi is mainly for boys. Girls’ celebration is held on March 3rd, Hinamatsuri, it is not national holiday though.