A koinobori, literally meaning“carp streamer,"is a carp-shaped decorative windsock made of fabric or paper. On May 5, which used to be known as Tango no Sekku, or Boys' Day, it was traditional for families with boys to celebrate the occasion by flying koinobori and to pray for their sons' healthy growth. It is believed that carp will swim upstream even against a waterfall, and so parents fly the streamers with the hope that their sons will make their way in life with the vigor of a carp. 意訳:布または紙で作られた鯉の形をした幟のぼりのこと.5月5日は端午の節句または男の子の日と呼ばれ,男の子のいる家庭では庭先に飾り,男の子の健やかな成長を祈願する.鯉は滝をも登るということからその勢いが好まれ,この風習が生まれたのだろう