Japan's legendary ninjas are famous for their stealth and were said to possess a supernatural gift for invisibility.
But now martial arts experts are concerned they might be disappearing in real life, as practitioners of the ancient "ninjutsu" say there is a major talent shortage.
As tourism to Japan has grown, there has been an increasing demand to see the iconic warriors perform “ninja shows” to crowds - but martial arts squads are struggling to find candidates who are up to scratch.
Takatsugu Aoki, the manager of a martial arts squad in the city of Nayoga in the south of the country, told the Asahi newspaper: “With the number of foreign tourists visiting Japan on the increase, the value of ninja as tourism content has increased.
“There are more employment choices, while ninja shows across the country have become popular. I feel there is a ninja shortage.”
Those who do put themselves forwards, he said, lack the basic skills needed. This usually means being trained in unarmed combat, acrobatics, concealment and first aid while also being able to use throwing stars and fight with swords.
Invisibility and walking on water, despite the folklore, are not part of the job description.
Although they have developed a reputation as fearsome warriors over the centuries, ninjas were primarily concerned with espionage during their heyday in feudal Japan.
Ninjas prided themselves first and foremost on their skills in spying and their endurance – violence was supposedly seen as a last resort.
But they were traditionally skilled in using weapons such as shuriken, known as throwing stars in the West, and the fukiya blowpipe which was usually filled with a poisoned dart.
They first emerged as mercenaries in the 15th century during an era of civil war known as the Warring States period and were recruited to act as spies, raiders, assassins or even terrorists.
Disdained by general society, which was based on a strict hierarchy with the elite samurai class at the top, they soon formed into guilds with their own sets of rules and ranks.
These guilds had different types of ninjas, or shinobi, assigned to specific tasks and they often controlled their own individual territories.