The Shanghai Adult Care Expo, a small gathering compared to some of China’s larger sex-toy industry conventions, is attended primarily by young men, gawking with their camera phones at the ready. They charge from booth to booth, snapping photos of the models. Between stops they pose for photographs with one of the show’s biggest attractions: a gigantic, rotating dildo.

Weaving through the crowd with clipped, efficient steps, a tiny Chinese woman stands out as a professional. She is better dressed, less hurried and infinitely less impressed. This is Mistress Wu, one of Shanghai’s most successful dominatrixes. “Ugh,” she says, brushing an idle hand along some flimsy-looking nurse and army uniforms. “Most Chinese dominatrixes are still wearing this stuff. It’s cheap and they look ridiculous.”

Mistress Wu is a compact person. She wears a knee-length leather trench coat, a tight maroon dress and a discerning look on her face. “You can skip all of these booths and go straight to Lelo,” she tells me, pointing out the line of upmarket Swedish sex toys. Their high quality silicon makes them perfect for her expertise: anal penetration. “All of this other stuff is too stiff. The goal is not to draw blood.”

In China’s cities, BDSM is a small but growing piece of the country’s sexual revolution. Following the 1990s, when attitudes started to change, premarital sex became more accepted and homosexuality was decriminalized, fetish parties and burlesque shows become regular fixtures in cities like Beijing and Shanghai. Dungeons are kept top-secret, but have been subject to the occasional newspaper expose. Chinese sex shops have graduated from fuzzy handcuffs to stocking restraints, whips and the occasional butt-plug. And an increasing number of Mistresses, like Wu, have been setting up shop in China’s more affluent cities.

Before heading for the expo, I met Mistress Wu in a bright, well-lit and popular brunch spot in Shanghai’s Jing’an District. She asked if she could bring along her friend, “Dave” and we sipped coffee while she talked about her lifestyle. “I am not a client,” said Dave, preemptively, holding both his hands up palms-forward. “I’m just interested in this kind of underground culture.”

The taboos around BDSM are global. Books like 50 Shades of Gray may be wildly popular, but they also portray the practice as a deviant behavior driven by childhood trauma. As a result, talking to Mistress Wu, it can be hard to separate how the challenges she faces as a Chinese dominatrix differs from the stigma a dominatrix might deal with elsewhere. Her family, for instance, thinks that Mistress Wu works as a sales representative in a trading company. But, when I ask her whether a Chinese dominatrix goes against the traditional stereotypes of Asian women, she says no. “Chinese women are naturally dominant!” Wu says. “Especially the women in Shanghai.”

As a professional dominatrix, Mistress Wu exists in dangerous territory in China. BDSM has grown in cities like Beijing or Shanghai, but most professionals work hard to avoid official attention. While prostitution and sex work in China is booming, recent crackdowns on the industry made headlines all over China. “The government goes back and forth. Many officials receive bribes from prostitution facilities like massage parlors and karaoke bars and the police turn a blind eye,” says Richard Burger, author of Behind the Red Door. At other times, however, the authorities will crack down. Most recently, a crackdown in the southern Chinese city of Dongguan hit over 2,000 clubs and bars and over 500 people ended up detained. “We’ll see if Dongguan was an isolated incident or a sign of things to come,” Burger says. “At the moment, the government’s attitude toward prostitution is difficult to define. It’s left it alone in big cities like Shenzhen and Shanghai.”

Like most dominatrixes, Wu is clear that she is not selling her body, but the distinction is no guarantee that she couldn’t run afoul of the law. She keeps a low profile, operating out of hotel rooms rather than opening a dungeon, and accepting only a few new clients every year.

Mistress Wu grew up in Nanjing (about 160 miles up the Yangtze River from Shanghai), and like many Chinese, was taught little about sex. “People in my school thought you could get pregnant by holding hands.” There wasn’t much opportunity to explore your kinks, but Mistress Wu believes domination has been a calling from childhood. “My mother was a Wushu master,” she says, talking about a brand of martial arts. “Maybe if she had trained me, I wouldn’t have ended up so interested in kink!”

Because information on sex is limited in China—no sex on television and an ongoing government crackdown against online porn—Wu says most Chinese people of her generation (she is in her late 20s) required a guide to introduce them to BDSM. She found one in a German boyfriend she met while in college at Nanjing University. At first, she says, she alternated between sub and dom, but it didn’t take long until she figured out what she really loved. She met another man interested in BDSM at a cluster of sex shops in Shanghai (“This is how I learned how to use needles,” she says.) and slowly started to build her expertise and her client base. “Working as a dominatrix is a kind of mind game,” she says. “It’s a mental exercise in exchanging power. You lose brain cells coming up with these scenarios and figuring out how to make them work.”

Some Chinese dominatrixes lean toward a cultural vocabulary that is distinctly Chinese (think PLA army outfits and Cultural Revolution-throwback scenes). Mistress Wu, however, prides herself on her Western sensibility. She specializes in needles, anal and, she says, creative mind control. (She is sadistic, she adds, but not a killer—her clients trust her.) Today, Mistress Wu’s client base is now almost entirely non-Chinese. “Chinese men are too into foot worship,” she declares during brunch, speaking over the din. Plus, promoting oneself to Chinese clients can be a nuisance. “You might put up a Chinese website and, if you’re lucky, it’ll stay up for over a week.” Instead, she advertises her services on an English website and on Western kink websites. “Most of my clients have been with me a long time,” she says. “They travel to Shanghai on business and look for me and, at this point, we are like old friends.” Her requested tributes start at $200 per hour, she says. “Most Chinese men wouldn’t want to pay that, anyway.”

In China, where prudishness and sexual liberation cause regular clashes, even Mistress Wu has something of a deadline for herself. By the time she is 35, she would like to be married. She is interested in someone who fills these conditions: “intellectual, fit, sensible, humorous, musical, pervert.”

In the meantime, business is booming. Walking around the sex show in Shanghai, Mistress Wu is setting up a date for later that night. “I would let you come and watch,” she says. “Public humiliation is sometimes a part of what I do, but this is the first time this client is asking for anal. I want to give him a break.” We wander into a section of the show that features a range of male chastity belts—penis-shaped metal cages that prevent the wearer from getting an erection. A large European man, bent over a particularly vicious-looking one, saw Mistress Wu and straightened up. He glanced at me for a long second and then shrugged slightly. “Well,” he said to her. “I guess now that you’re here I won’t have to forward you the photos I’ve been taking of the stuff I like.” Later, Mistress Wu sent him a text: “I’m so proud of you,” it read, in English. “For being so open.”

This is the third and final piece in our Sex in China Series. Read Monday’s on China’s only certified sex coach and yesterday’s on Beijng’s most innovative sex shop.

Lauren Hilgers is a reporter specializing in China who has written for Harper’s, Wired, and Bloomberg Businessweek.