The Koinobori are a flown above the house at this time of the year. The Carp is a strong, powerful swimmer, and symbolizes strength and singleness of purpose. May 5th used to be boy's day, with March 3 being a festival primarily for girls. Boys still display the Samari dolls on this day. Families fly the Koinobori originally only for boys, but now symbolizing the family.