Kodomo-no-hi, or Children's Day, falls on May 5 of every year. One of the most popular national holidays, Children's Day actually started long ago as Boy's Day, a holiday celebrating male Children. Today people have enlarged the festivities to include children of both genders, but much of the old trappings and decorations are carry overs from Boy's Day.

To drive away bad luck and bring good fortune to children, a family will hoist koinobori (colorful cloth carp streamers) from flagpoles or other high places. The koi (carp) is thought to symbolize strength and endurance since it is able to swim upstream even against a forceful waterfall.