The first week of May is a special time in Japan. Golden Week (April 29–May 5) consists of seven days of holidays, including Shōwa Day, Constitution Memorial Day, and Greenery Day. On the final holiday of the week, Kodomo no Hi, something amazing happens: the sky glitters with thousands of flying fish. Koinobori, Japanese carp streamers, that is.

Kodomo no Hi, or Children’s Day, is a modern version of Tango-no-Sekku, an annual ceremony that took place on the 5th day of the 5th moon of the year from the 6th century to the late 19th century. After Japan switched from the lunar calendar to the Gregorian calendar, May 5th was permanently established as Boy’s Day.

There are a few different stories about the origins of Boy’s Day, but both come to the same conclusion: The day was created in order to celebrate boys and their fathers and to wish for a year of healthy growth for the kids. In 1948, the holiday was modified to include girls and their mothers and thus became a celebration of all children.

Kashiwa mochi—mochi wrapped in oak leaves.
Koinobori, carp-shaped windsocks, are used on Children's Day because the fish is a symbol of courage, luck, and vitality, and because carp are not just colorful but resilient, able to swim upstream through powerful currents and even waterfalls. Parents fly koinobori both to honor their children and to wish for their growth. 


As the skies fill with koinobori, other decorations also pop up across the country. Samurai helmets and samurai dolls are set out for display, and iris flowers are placed on tables full of special Children’s Day eats like kashiwa mochi, a mochi rice cake wrapped in oak leaves, and chimaka, a dumpling wrapped in bamboo leaves. School's out for the day, and families often go to special events such as children’s theater performances and parades. It’s a beautiful end to a week of big celebrations.

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