May 5th is Children's Day in Japan celebrated by families flying colorful koinobori carp streamers to celebrate the health and vitality of their children and grandchildren.
In Japan the koi (carp) has come to represent strength, courage, endurance, perseverance, and health, and these attributes gave been derived from a well known, ancient Chinese tale of a golden carp that swam upstream of the Yellow River, eventually swimming up a waterfall and being reincarnated as a dragon.
The qualities attributed to the koi were those most valued by the samurai and wished for for their sons.