Kodomo no hi or Japanese Children's Day is a festival originally for boys ("tango no sekku") but which has been renamed for both sexes and is held on the 5th day of the 5th month. On this day families with newborn sons fly koinobori, beautiful multi-colored carp windsocks outside of homes to wish their sons a good future. Otoko means "boy" and sekku means "festival". The festival originated in China and later became associated with May rice planting in Japan.
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Carp streamer, Koinobori 鯉のぼり for Children’s Day 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 Japan, Children's Day is heralded by the appearance of flying fish known as Koinobori. Make a carp-shaped windsock to fly in the breeze outside your home! http://www.dickblick.com/ProjectIdeas/Koinobori-Windsock/