Masters in the dark arts of espionage and silent assassination, they are rarely seen and never heard... until they strike.
Employed by samurai warlords to spy, sabotage and kill, they are relics of an ancient code that have all but died out in the modern age.
All but one. As the 21st head of the Ban clan, a dynasty of secret spies that can trace its history back some 500 years, 63-year-old engineer Jinichi Kawakami is Japan's last ninja.
He is trained to hear a needle drop in the next room, to disappear in a cloud of smoke or to cut a victim's throat from 20 paces with nothing more than a two-inch 'death star'.
Death stars: Jinichi Kawakami demonstrates the traditional Japanese concealed weapon the 'shuriken' at the Iga Ninja Museum
'I think I'm called (the last ninja) as there is probably no other person who learned all the skills that were directly handed down from ninja masters over the last five centuries,' he said. 'Ninjas proper no longer exist.'
But Kawakami has decided to let the art die with him because ninjas 'just don't fit with modern day', adding: 'We can’t try out murder or poisons. Even if we can follow the instructions to make a poison, we can’t try it out.'
An engineer by trade, Kawakami started practicing the art of Ninjutsu at the age of six before he began training under the gruelling regime of Buddhist master Masazo Ishida.
To improve his concentration, he would spend hours staring into the flame of a candle until he felt he was inside it.
Silent and deadly: Kawakami is trained to hear a needle drop in the next room, to disappear in a cloud of smoke and to cut a victim's throat from 20 paces with nothing but a three-inch death star
Tough training: As part of his training, Kawakami climbed walls, jumped from heights and learned how to mix chemicals to cause explosions and smoke and was also trained to withstand extreme heat and cold as well as go for days without food or water
To hone his hearing he would practice listening to a needle being dropped onto a wooden floor in the next room.
THE ART OF STEALTH: HOW NINJAS WERE REVERED THROUGH HISTORY AS ASSASSINS, SCOUTS AND SPIES
Ninjas, also known as shinobi, have been feared and revered throughout history for their talents as assassins, scouts and spies.
They are mainly noted for their use of stealth, their dark outfits usually covering everything but their eyes, leaving them virtually invisible in shadow, until they struck.
But they were also known for their amazing powers of endurance.
Ninjutsu can be translated as ‘Art of Stealth' but also means ‘Art of Enduring'.
The ninjas themselves were noted for being able to walk long distances without stopping, jump over seven feet and dislocate their joints to escape from small spaces.
But they were not only ruthless killers as depicted in so many Hollywood movies.
In fact, ninjas considered the art of espionage far greater than that of fighting which was always a last resort - ninjas were skilled in spying and defeating foes using intelligence, while swinging a sword was deemed a lower art.
And they were also skilled at making poisons as well as potions and medicines.
He climbed walls, jumped from heights and learned how to mix chemicals to cause explosions and smoke.
He was also trained to withstand extreme heat and cold as well as go for days without food or water.
'The training was all tough and painful. It wasn't fun but I didn't think much why I was doing it. Training was made to be part of my life,' he said.
And at the age of 19, he inherited his master's title along with a cache of secret scrolls and ancient tools.
But he says the art of the ninja lies in the power of surprise, never brute force or outward strength and is about exploiting weaknesses to outfox larger, more powerful opponents while distracting their attention to get the upper hand.
And, he says, the ability to hide in the most unlikely of places is a ninja's greatest weapon.
'If you throw a toothpick, people will look that way, giving you the chance to flee, he adds. 'We also have a saying that it is possible to escape death by perching on your enemy's eyelashes; it means you are so close that he cannot see you.'
Kawakami now runs the Iga-ryu Ninja Museum, in Iga, 220 miles southwest of Tokyo and recently began a research job at the state-run Mie University, where he is studying the history of ninjas.
He says he has decided not to take on an apprentice to pass on the legacy, making him the last in the line of Ban clan ninjas.
Ninjas, also known as shinobi, have been feared and revered throughout history for their talents as assassins, scouts and spies.
They are mainly noted for their use of stealth and deception but also for their amazing powers of endurance.
Inside the flame: To improve concentration, he would spend hours staring into the flame of a candle until he felt he was inside it and would practice listening to a needle being dropped onto a wooden floor to hone his hearing
Heart-stopping: The 'ninja performance unit', perform their skill during a ninja show at at the Iga Ninja Museum
Ninjutsu can be translated as ‘Art of Stealth' but also means ‘Art of Enduring' and the ninjas themselves were noted for being able to walk long distances without stopping, jump over seven feet and dislocate their joints to escape from small spaces.
But they are not only ruthless killers as depicted in so many Hollywood movies.
In fact, ninjas considered the art of espionage far greater than that of fighting which was always a last resort - ninjas were skilled in spying and defeating foes using intelligence, while swinging a sword was deemed a lower art.
But if necessary, they had to be experts with weapons such as shuriken, a sharpened star-shaped projectile, and the fukiya blowpipe, usually filled with a poison dart.
And they were also skilled at making both poisons and medicines.