Koinobori

Koinobori (鯉幟^?), meaning "carp streamer" in Japanese, are carp-shaped wind socks traditionally flown in Japan to celebrate Tango no Sekku (端午の節句^?), a traditional calendrical event which is now designated a national holiday; Children's Day.^[1]

These wind socks are made by drawing carp patterns on paper, cloth or other nonwoven fabric. They are then allowed to flutter in the wind. They are also known as satsuki-nobori (皐幟^?).
Children's Day takes place on May 5. Landscapes across Japan are decorated with koinobori from April to early May, in honor of sons and in the hope that they will grow up healthy and strong.

In 1988, a 100 m long koinobori weighing 350 kg was made in Kazo, Saitama.

There is a famous short Koinobori Song often sung by children and their families:
Japanese:
屋根より高い鯉幟
大きい真鯉はお父さん
小さい緋鯉は子供たち
面白そうに泳いでる

Translation:
Higher than the roof-tops are the koinobori
The large Carp is the father
The smaller Carp are the children
They seem to be having fun swimming