The fifth of May is Tangonosekku, Boys Day Celebration; a time to pray for young boys to grow up strong and healthy. Families with young boys celebrate by eating cake wrapped in bamboo leaves or rice cakes wrapped in oak leaves, flying carp banners, and wearing helmets.
Because the Japanese iris (Joubu) blossoms in May, the celebration is also known as Jobunosekku.
Long ago, medicinal plants were harvested on the day the seasons changed, and people prayed for good health. The Japanese iris (shobu) was used as a medicinal plant, and because it had the same pronunciation as the Japanese words for 'fighting spirit' and 'victory,' the word came to be used to pray for strength and good health for young boys.

Carp banners came from the Chinese tradition of toryumon, or 'gateway to success.'
There is a place called Ryumon (Dragon's Gate) on the Yellow river in China. It was said that carp fighting up their way up the rapid currents became dragons here. Because of this legend, families fly carp banners and pray for the success of their boys.