Colourful carp-shaped streamers fluttered all over Japan on Thursday as an increasingly elderly nation readied to pray for the health of young sons and mark Children's Day.
The large fish flags, which inflate with the breeze like a windsock, are hung in towns and villages all over the country, with many strung across rivers.
Tango no Sekku (Boys' Festival) coincides with Children's Day, a national holiday that this year falls on Sunday, but which will give Japan's salarymen a day off on Monday as part of the "Golden Week" holiday period.
It comes around two months after Girls' Festival, when families decorate their homes with ornate dolls to pray for the well-being of daughters.
In Sagamihara, a city west of Tokyo, some 1,200 "koi nobori" streamers flapped across the river, an organiser told AFP, adding they were hoping to see around 400,000 visitors over a week.
The Boys' Festival is believed to have started in the Edo era, which spanned from the early 17th to the mid-19th century, when commoners began flying carp-shaped streamers after the birth of a son.
The carp -- "koi" in Japanese -- is a symbol of health, prosperity and success, reflecting the fish's ability to leap small waterfalls as it swims upstream.
Other customs remain to mark the festival, including decorating the house with a doll in samurai armour and bathing children in a hot tub with iris leaves.
People aged 65 or over make up around a quarter of Japan's approximately 128 million population. The elderly are expected to account for 40 percent of the population in 2060.