It's the biggest mystery on the internet in China today.
Tens of thousands of people have been signing up to follow a Sina Weibo microblog account - China's equivalent of Twitter - that seems to have inside access to the new Communist Party leader Xi Jinping.
But who exactly is the mysterious "fan" who seems to be at Xi's side recording his every step? Is it really a simple "fan"? Or is it all a cunning PR ploy to burnish Mr Xi's image? And where might it lead?
The account goes by the name "Hao Hao Xue Xi" - a play on a Mao-era slogan and Mr Xi's name, it translates as "Study Hard", or the "Study Xi Fan Club". Here's a link, but you have to sign up for a Weibo account to be able to see it.
It's remarkable for the close-up, up-to-date images it posts of China's new leader, sometimes in apparently intimate moments. On Wednesday there was a photo of an obviously poor, elderly man clutching the hand of a smiling Mr Xi in front of a mud-walled house. Mr Xi is dressed in a simple, sober outfit.
He has been on a visit to a poor area of Gansu province. The moment is clearly spontaneous, but it looks like a publicity shot. The message isn't hard to decipher, Mr Xi is meant to look very much the caring leader, out and about to get in touch with ordinary people.
On 4 February there's something more unusual, a photo of Xi Jinping apparently snoozing in the front seat of a minibus while touring Gansu. It's taken from outside, snapped through the window, so it looks spontaneous again.
Usually nobody ordinary gets this close to a Chinese leader, and not even state media publish such unguarded shots. But it has a clear purpose, Mr Xi is shown not in a fancy limousine but an ordinary bus, reinforcing the message he's been giving that officials need to eschew luxury and extravagance. The other message is that this is a leader who works hard.
The caption the blogger has added to the photo is fawning. "He's been out and about for the past few days, he's very tired .. we young people are exhausted after running around for a day, not to mention someone like Xi who is almost in their sixties. Uncle Xi, please take care of your health. And when you appoint local government officials, choose capable ones so they can share your burden."
The blogger keeps adding details about Xi's movements. On 5 February at 11:05 he wrote: "Xi has arrived back at his hotel." On the 4 February at 11:40 he wrote: "Xi is visiting old people in an old people's home."
It's the sort of access to a national leader most journalists in China can only dream of. The movements of China's Communist hierarchy are a closely guarded secret, and only carefully screened pictures are released after most events.
The "Fan Club" began posting shortly after Xi Jinping was promoted to become general secretary of the Communist Party last November. At the start of this week it had 130,000 fans. But by Thursday numbers had soared to more than 490,000.
At times it has been way ahead of even the official news outlets. China's national TV news service, CCTV, posted a slightly miffed sounding comment on its own microblog asking: "What happened? The Study Xi Fan Club is quicker and closer to him than us."
Some think it's the slightly unsubtle work of Xi Jinping's own PR team, an aide or an official, trying to use the internet to shape his image as he prepares to take over as president.
On the 5 February the "fan", who says he's a young man from Shaanxi province, posted a message to claim: "I am just a normal internet user. I am working class. My company has given us time off for Chinese New Year, that's why I have time to follow Xi's movements. As a fan I care about him a lot. I am not a Communist. I am not a government official. I have nothing to do with his team."
He went on: "Every president has their own fan site, Obama, Putin .. it's my right to be a fan of whoever I like."
But most observers think it's inconceivable that this is just a random "fan" taking all these pictures. Another this week showed Xi in an ordinary canteen eating a simple meal. Coincidentally Mr Xi has recently called for Communist Party officials to give up on extravagance and there's an official campaign to clamp down on excessive banquets which waste huge quantities of food.
Or this week there was also Xi Jinping, again out in a rural setting, at the back of a crowd of people, humbly not pushing himself to the front. No ordinary Chinese citizen would be able to follow Xi to so many events.
There are now more than 500 million internet users in China. The internet is still heavily censored and foreign sites like Twitter and Facebook remain blocked. Three hundred million people use China's own microblog services. If they step over the line their posts are quickly deleted by an army of censors, but there is still much freewheeling debate and criticism that gets through.
So it seems likely the "Fan Club" is an attempt to give Xi Jinping a presence online. Many arms of China's government from police forces to local governments operate thousands of microblogs to ensure they have a voice.
But the question now being asked is whether the effort will go further. Will Xi Jinping himself venture online, openly? Will he dare to start up his own microblog? Or at least an official one operated by his office.
It's an intriguing prospect, but it would be a risky step as it would plunge China's leader into a world where many are highly critical of the Communist Party. Online people are often scathing in their opinions and highly inventive in the ways the find to pour ridicule on officials.
China's leader might also find himself deluged with complaints, grievances and suggestions from ordinary people, sent directly to him but visible to all on the internet. How would he deal with that? "Petitioners" who try to send letters or bring their grievances in person to the leaders in Beijing are already treated as a nuisance by many officials and are frequently rounded up. Trying to be more open online might backfire
China's Communist Party has ingrained habits of censorship and control when it comes to information, the media and the internet, changing those will be hard. Running a "Fan Club" is the easy option.