TOKYO, Japan - In the concrete jungle of Tokyo, some 600 retirees have gathered to fight for supremacy - with blow darts.
The ancient Borneo rain forest tradition of blow darting is picking up new fans thousands of kilometers away in Japan, where it is a rapidly growing sport among the nation's elderly.
In just five years, nationwide membership in a blow dart club has tripled, on target to hit 30,000 members this year. The average age of enthusiasts is 70.
"Older people are really getting into it because it's easy for anyone to do - whether your legs are playing up, you're confined to a wheelchair or missing an arm," said Nobuhiko Yamada, a blow darting instructor.
"In fact, you can do it even if you have no arms. It's just that little puff of air."
Though popular culture has placed blow darting - or "fukiya," as it's known in Japanese - among the arsenal of ninjas and nighttime assassinations, actual historical records of it are few.
The meditative movements of the sport that the elderly now enjoy were created in 1998 by a Japanese man looking to liven up his daily breathing exercises.
Gathering in a gymnasium, they insert plastic darts - with blunted tips - into .51 caliber, 120 centimeter-long hollow poles, and shoot them at a target.
"It's different because you can do it at a pace that suits your own body. It's down to the individual, not a group activity," said 79-year-old Yoko Onmyoji.
Popularity of the sport is likely to grow still further, given Japan's rapidly graying population. By 2060, the number of people aged 65 or older is expected to hit 35 million, nearly 40% of the population, compared to 23% in 2010.
The sport is especially popular among Japanese men, who tend to be a bit lost after devoting their lives to their jobs, Yamada said.
"After they retire they don't know what to do, they don't know anyone in the local area. When they find out there's this fun sport catering to the elderly, they jump at it," he said.
But most simply take part for fun.
"When you get to this age, you can't really do most sports. But blow darting's easy to do," said Tomotaka Kajitani, 81. "Well, it's a bit easier, at any rate."