Their banners have urged an end to China's "dictatorship", scorned the regime as "rogue" and dared leaders to disclose their assets as a step against graft -- all dangerous calls under Communist Party rule.
The Southern Street Movement, a loose network of laymen-activists in Guangdong province, is testing China's limits with overtly political demands and ambitions to inspire placard-waving protests nationwide.
The province has a tradition of defiance -- a trade hub long exposed to the outside world, it was the birthplace of Sun Yat-sen, the revolutionary who ended millennia of imperial rule in China in 1911.
Yet the dissent-wary government has mounted a growing crackdown on activists this year and a smattering of participants have been detained.
Protesters must overcome their fear, says Xie Wenfei, a 37-year-old from central China whose business card declares him a "Southern Street Movement activist" and proclaims: "If you see injustice and remain silent, you have sided with evil".
He raised a sign calling for an end to "one-party dictatorship" in the provincial capital Guangzhou in September, earning himself a month in detention.
"Lots of friends called me to say if you pull out this banner then for sure you'll be arrested," he said. "But I had to do the right thing. I told them someone has to do this.
"First I wanted to tell my like-minded friends to break through the fear.
"Second I wanted to tell the Communist Party that the way they are doing things cannot last. They have lost their legitimacy in the eyes of the people and the law."
The movement started in 2011 with monthly protests at a park, said Wang Aizhong, a closely involved 37-year-old businessman, and they organised mini-rallies perhaps dozens of times this year.
Many have called for officials to reveal their assets, for detained activists to be released, and for an end to one-party rule.
"We see the Southern Street Movement as a resistance movement having no organisation, no leader and no formal programme," Wang said, adding that they wanted to "inspire the rest of the country".
"There is no one single or set demand, but a lot of the political demands are aimed at one goal, which is to end this dictatorship."
The movement has mostly attracted the migrant workers who have flocked to Guangdong, a manufacturing powerhouse and China's most prosperous province.
More people were drawn in following January protests supporting the liberal Guangzhou-based newspaper, Southern Weekly, after its new year editorial was censored.
'I have never done anything wrong'
Guangzhou has long been considered less strictly controlled than much of China.
It has had greater contact with the rest of the world as one of the first Chinese cities opened in recent centuries to foreigners -- who knew it as Canton -- and Guangdong neighbours the former British colony of Hong Kong.
"There is a perception that protest is just slightly more possible in the south," said Eva Pils, an associate professor at the Chinese University of Hong Kong.
"More people in the south are willing to take that one further step and actually put up a banner that directly targets 'one-party dictatorship', that directly calls for constitutional government, freedom, human rights, democracy."
But the consequences of activism in China can be severe. In neighbouring Jiangxi province three members of the similarly loose, decentralised New Citizens Movement face up to to five years' jail for demanding officials disclose their assets.
Such grassroots groups are at the opposite end of the activist spectrum from internationally high-profile figures such as Nobel laureate Liu Xiaobo, artist Ai Weiwei or blind lawyer Chen Guangcheng.
They are among a number of Chinese looking to have their voices heard, including online. But the groups' numbers remain tiny and it is impossible to judge their support in a heavily controlled society.
Southern Street member Jia Ping, 24, lost his factory job after posting political messages online, and was detained for 20 days after displaying signs at a train station including one proclaiming "the Communist party does not represent the people".
"We will definitely keep going, as far as we can," he said.
In August officials detained respected Guangzhou activist Yang Maodong, known by his pen name Guo Feixiong.
He finished a five-year sentence in 2011 and now faces public order charges carrying a similar maximum penalty.
Authorities see him as a ringleader, said his lawyer Sui Muqing, citing an editorial in the party-run Global Times criticising Guo and another activist, a rare reference to such figures.
"They pose a danger to the current social governance system and long-term social stability," the paper warned. "Confronting the authorities has become their way of life."
Migrant Xie said his parents want him to stop his activities.
"Of course they are afraid," he said. "I just ask them to trust me. I'm over 30 years old and have never done anything wrong."