Carp Streamers What Is The Gist Of The Story Of The Japanese Children's Book "Oyoge Ookina Koinobori (Fly, Big Carp Streamer)?

What is the gist of the story of the Japanese children's book "Oyoge Ookina Koinobori (Fly, big carp streamer)? - carp streamers

Then you are on a URL, please add that I read online, or you tell me the essence of the story. Thank you.