A craving for fast food presents few obstacles to most people, but for Japan's dainty, doll-like geishas, it calls for a daring undercover operation -- and a cunning disguise.

While strictly taboo for a geisha to be seen munching French fries, some "geiko" -- as they are known in the ancient city of Kyoto -- and their young "maiko" apprentices have hatched a clever plan to avoid detection.

"It's necessary to be very careful about the image we project," celebrated geiko Kikumaru told AFP in an interview, kneeling on the floor of a wooden teahouse in the fabled entertainment district of Gion.

"A maiko is basically banned from going into fast-food restaurants, or trendy stores selling short skirts. But sometimes they just crave fried potatoes," she smiled.

"When they do, we have to put on a pair of jeans and go and buy them some, and let them eat at home in secret."

In the cloistered world of Kyoto's five geisha quarters, known as "hana-machi" (flower towns), seemingly little has changed since their rise in the 17th century.

"It is a geiko's duty to protect Japanese customs and culture which are dying out, and to continue those traditions," explains Kikumaru in the soft regional dialect.

"When we go outside, we must always be careful about how we walk, our posture, our behaviour. No, we're not allowed to be on Facebook or things like that."

- Geisha yoga -

Adorned in crisp kimonos, their faces powdered white, geishas float elegantly along Gion's cobbled streets between engagements at the district's quaint, but cliquish, teahouses.

Skilled in Japanese arts such as dance, the lute and three-stringed shamisen, the job of a geiko -- performing girl -- is to entertain exclusive guests, normally over dinner or at banquets.

Their clients are often high-profile politicians or businessmen, who do not even know how much a night costs until they receive an eye-watering monthly bill.

"People think it's glamorous but it is a test of strength," Kikumaru said with a giggle.

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"It's hard work but geishas are made of hard stuff, very determined and strong women. Some go to the gym. I do yoga, or did. You really don't get enough free time."

Kyoto's geikos begin as maids after completing Japan's compulsory education at the age of 15, soon becoming maiko -- dancing girls.

They spend the next five years training in performing arts, gracious social etiquette and conversation skills. Usually at around 20, they assume the title of geiko.

However, the strict convention governing the life of the some 175 geikos currently working in Kyoto sits in stark contrast to the freedom and mod cons enjoyed by the upwardly mobile women of modern Japan.

It is a divide Kikumaru, now 31, is acutely aware of.

"You are constantly aware you're living a life which is not a normal one," she nodded. "You're coloured by this lifestyle as a geiko and you do feel a disconnect with the general public."

"If a maiko on her way to a banquet in her kimono sees schoolgirls of the same age in their uniforms, she will imagine them going off to eat dinner together while she's sitting on a tatami floor. She doesn't have any private time and shares a room with three or four other girls.

"You sacrifice your teenage years training to become a geisha and sometimes you can feel you want to give up. But you have to conquer those feelings."

Perceptions of geishas are often far from reality.

- Gilded world -

Many among Kikumaru's profession were horrified by the novel -- and 2005 Hollywood hit movie -- "Memoirs of a Geisha" whose subject, the former geisha Mineko Iwasaki, sued the book's writer Arthur Golden for allegedly likening Kyoto's famed hostesses to prostitutes.

"There are even Japanese people today who don't fully understand a geisha's craft," added Kikumaru, referring to the mystique surrounding her gilded world.

"Movies exaggerate, of course. What specifically is it that's different between that movie and a real-life geisha? Well, basically everything!" she laughed.

"There are women who perform very different jobs to a geiko but somehow we were all painted the same colour."

While some past geishas in other parts of Kyoto and Japan offered sex, those in Gion complain that foreigners often mistake them for prostitutes because of their showy outfits.

"There is no physical intimacy," insisted Kikumaru. "A geiko is a confidante."

But if gender equality appears alien to this fantasy time warp, think again.

"Geishas in Kyoto were once daughters of samurai warriors," said Kikumaru.

"When the feudal system collapsed, these girls from military stock naturally possessed the social graces and became entertainers to support their families. They were the rock of the family."

Walking with tiny steps, a geisha nonetheless follows three steps behind a man.

"It's quite natural," said Kikumaru with a playful frown.

"In Japan, gentlemen don't walk ahead because they believe they rule the roost. It used to be dangerous to walk outside as people carried swords (so) men walked in front to protect the women from getting slashed -- it's very chivalrous!"