Soya no Sohi attracted tens of thousands of Twitter followers as a pretty, young motorcycle enthusiast burning up the scenic roadways of northern Japan, posting daily photos as she journeyed across mountains and beaches on her classic Yamaha sport bikes.

Then in March, the social media darling came clean: Soya was actually Yasuo Nakajima, a 50-year-old man who had used the iPhone app FaceApp to transform his face in every shot. The more than 300 selfies he had posted since last summer — the ones with the dewy skin and the perfect smile — were all computer-generated fakes.

His reveal ignited a Japanese media sensation: the “ultimate catfish” who had fooled the Internet into adoring an imaginary woman. Nakajima told a variety show he’d adopted the persona because no one wants to read what a normal middle-aged man posts.

Then something unusual happened: His follower count soared. His fans didn’t voice betrayal or alarm over the year-long fraud; many said they had cared more about his personality than his face. “This beautiful woman only exists within Soya-san,” one Twitter account said, attaching a genderless Japanese title connoting respect. Said another: “I’ve come to like you even more.”

With a few taps, Nakajima had capitalized on a popular kind of artificial intelligence with a strange power to warp the world. Millions have used such “facial filters” to erase their wrinkles, revamp their hairstyles and "enhance” their appearance in photos — mostly so they could post them on social media, where they could be tagged, analyzed and ranked by shares and likes.

But Nakajima had pushed the technology to its natural conclusion: He hadn’t just refined his face, he’d invented a new one. With it, he had gained the trust and affection of a bunch of strangers who had no clue who he really was. And since his unmasking, he’s been posting more than ever as smiling Soya, carrying on the fantasy.

To Nakajima and his fans, Soya’s fame illustrated a simple truth: that social media is less a reflection of who we are, and more a performance of who we want to be. In a video call with The Washington Post one Saturday night last month from his home in Japan, his first international interview, Nakajima said the charade had helped him express a side of his personality he’d been afraid to show the world.

“When you’re young, you tend to be scolded or criticized by older people who say you should do this or you should do that. But at this age, there’s no one around to really scold me,” he added, his low-pitched voice giving way to a slight laugh. “I’m having the best time of my life.”

Nakajima’s story casts a spotlight on the growing tension over identity and authenticity that has flared in the online age: What should we expect from the people we meet on the Internet, where algorithms can turn practically anything into a facade?

It also seemed to herald a darker future where our fundamental senses of reality are under siege: The AI that allows anyone to fabricate a face can also be used to harass women with “deepfake” pornography, invent fraudulent LinkedIn personas and digitally impersonate political enemies.

Nakajima hadn’t needed to write code or orchestrate a dastardly plan to persuade people to follow a mirage. He’d just installed a free app that schoolkids and bored adults around the world use every day for laughs. No law out there would stop him, or anyone, from doing it anywhere else. How many other Soyas are out there, building a following, living a digital lie?

Nakajima does not fit the mold of a typical Internet catfish. The divorced father of three and former competitive bodybuilder lives alone in Ibaraki Prefecture, a rolling expanse of coastal countryside northeast of Tokyo. Where many have converted garages into homes, Nakajima has done the reverse, turning his wood-paneled living room into a parking lot for his Yamahas: a TZR250RS sport bike, a WR250F off-roader and an XT1200Z Super Ténéré touring motorcycle, surrounded by wrenches and sprays.

Nakajima has been riding and fixing up motorcycles since he was a teenager, vanishing on long road trips across the island’s flowering hillsides and waterfront highways. The “Soya no Sohi” name translates to “Soya’s Blue Ice,” a nod to one of Nakajima’s favorite winter rides at Cape Soya, on Japan’s northernmost point: He straps on spiked tires and races along the coast, the wind sweeping away the snow to uncover the ice beneath.

“Motorcycles are like a family member for me,” he said during the Zoom interview, wearing a racing jacket and a large charm necklace he’d gotten from a local market during one of his rides, his long hair pulled back in a ponytail. “I love the freedom. … When I travel, I am out for basically about two weeks to a month, and I don’t decide on a destination. I like to think, 'I’m going to go west this time,’ or ‘I’m going to go north this time,’ and then just depart.”

He had wanted to share his memories, so in 2019 he joined Twitter, uploading photos of picturesque landscapes and mechanical projects. After a few months, he had netted six followers. It all seemed a bit sad.

So last summer, while touring Japan’s Shikoku island, he tried something different. He had seen his children — one in college, the other two in high school — playing with FaceApp, so he tried it, posting a manipulated photo of himself as a young woman with radiant skin, flashing a peace sign with grease-stained gloves. For his Twitter handle, he chose @azusagakuyuki — a mash-up of the names of his kids.

Soya posed at the foggy peak of Mt. Nakadake. She relaxed with a burger and a Budweiser at an American-themed restaurant near Nagasaki. She catalogued the full disassembly and rebuilding of a TZR250RS, the same model of sport bike Nakajima had started riding 30 years ago — every screw replaced; every photo run through FaceApp. She even adopted a catchphrase: “Life is once. Play this world.”

As the photos began receiving hundreds of likes, Soya’s personality and style began to come through. She was relentlessly upbeat. She never sneered or bickered or trolled. She explored small towns, savored scenic vistas, celebrated roadside restaurants’ simple meals. She took pride in the basic things, like cleaning engine parts. And she only hinted at the truth: When one fan told her in October, “It’s great to be young,” Soya replied, “Youth does not mean a certain period of life, but how to hold your heart.”

She seemed, well, happy, and FaceApp had made her that way. Creating the lifelike impostor had taken only a few taps: He changed the “Gender” setting to “Female,” the “Age” setting to “Teen,” and the “Impression” setting — a mix of makeup filters — to a glamorous look the app calls “Hollywood.” Soya pouted and scowled on rare occasions when Nakajima himself felt frustrated. But her baseline expression was an extra-wide smile, activated with a single tap.

With thousands now following Soya, Nakajima played her up, referring to himself with feminine pronouns and crafting flowery messages dotted with Kaomojis, the little face expressions most often used by young women.