Koinobori (鯉幟/こいのぼり, Koi-nobori meaning "carp banner" in Japanese, are carp-shaped wind socks traditionally flown in Japan to celebrate Children's Day. 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/さつきのぼり, satsuki-nobor.
A koinobori set consists of, from the top of the pole down, a pair of arrow-spoked wheels (矢車, yaguruma) with a ball-shaped spinning vane, flying-dragon streamer (飛龍吹流し, hiryū fukinagashi) that looks like a windsock a black koinobori and a red koinobori. If more boys are in the household, an additional blue, green and then purple koinobori are added. The red koinobori's color can be varied as orange or pink. These carp sets are flown above the roofs of houses with sons, with the biggest (black) koinobori for the father, next biggest (blue) for the eldest son, and ranging down to the smallest carp for the youngest son.
The above information on the Koinobori was taken from the net and I took the above photo on our way home through a small village