In Japan, where Boys’ Day originated, the holiday was joined with Girls’ Day to form Children’s Day. However, Hawaii set aside separate days for both sexes. Hence, Girls’ Day is observed on March 3, while Boys’ Day falls on May 5.

A common sight in Hawaii’s neighborhoods during Boys’ Day is koinobori, large carp streamers or windsocks that “swim” in the tradewinds on bamboo poles in front of homes. Following tradition, each streamer represents a male in the household. The carp nearest the top of the pole usually symbolizes the father, and is the largest. Additional carp represent sons ordered by age, working downward from oldest to youngest.

Carp are classic symbols of masculinity in Japanese culture, associated with strength, perseverance and longevity. In the wild, the fish swim against the currents, scale waterfalls and live an exceptionally long life—qualities that are fitting traits for a young man.