Children's Day in Japan, held on May 5th. A time for families to celebrate the joy of a child, a tradition celebrated since ancient times. May 5th was traditionally a boy's holiday known as Tango no Sekku, when boys would fly carp-shaped flags and streamers, called koinobori (as depicted on this card). The family flies one carp flag for each son. The eldest son gets the largest flag and the youngest gets the smallest. There is also a black carp flag for the father and a red carp flag for the mother.