The koi is a fish that swims upstream, and can even leap out of the water over small obstacles.
Each coloured Koi streamer has its own meaning
Children’s Day 「kodomo-no-hi, こどもの日」 is on the final day of the 7 days Golden Week public holiday period in Japan.
The koi streamers are made like a reverse wind sock, with a small opening at the top end at the mouth of the fish, and a larger opening at the other end, at the koi’s tail fin.