The following evening, Hong Kong’s government was told that China’s Communist Party-controlled Parliament would take the extraordinary step of ruling on the legality of her oath, which was already being argued in a local court. Beijing has never intervened in a Hong Kong court case without being asked by local officials or judges before, raising alarms that the city’s considerable autonomy from the mainland, guaranteed by an international treaty, was being undermined.
Beijing is also outraged about a trip that Ms. Yau and her colleague, Sixtus Leung, known as Baggio, took to Taiwan last month to meet with pro-independence students there.
But for now, she and her young staff are settling into spacious offices on the 10th floor of Hong Kong’s Legislative Council building. Bottles of wine and Belgian beer, and three large megaphones, lay strewn about the messy office during a visit late last week. On her desk was a copy of “The Godfather,” by Mario Puzo, which she is eager to read.
On a whiteboard, written with blue marker, was the now-famous variation of “China” she had voiced at her inauguration. From the window next to her desk, the local headquarters of the People’s Liberation Army looms.
It was the road in front of the army headquarters — a building which also served as a British military installation — where Ms. Yau’s transformation began two years ago, on Sept. 28, 2014. It was there and then that she first experienced the political life: joining thousands of people in a standoff against the police.
As remarkable as Ms. Yau’s rise from office worker to radical lawmaker may seem, her personal transformation is far from unique here. She is just one of hundreds of thousands of Hong Kongers whose lives were altered by the pro-democracy protests that swept the city two years ago.
A generation of young people forged their political identities as they rallied — ultimately unsuccessfully — against China’s decision to put strict controls on planned elections for the city’s chief executive. To them, it was a betrayal of the promises made more than a generation ago that led to Britain transferring sovereignty to China, with the promise that Hong Kong would enjoy a high degree of autonomy until at least 2047.
“All of us had the same mission, that we had to stop the government and try to get our democracy,” Ms. Yau said in an interview.
After a few days, she became disillusioned with the main body of protesters who had set up camp on the thoroughfares around the Legislative Council building and the main government offices. The atmosphere was like a “festival,” she said.
“When I came out from my home I thought I had to fight, to have a war with the government,” Ms. Yau said.
When the protests ended after 79 days in December 2014, most participants resumed their daily routines. But not Ms. Yau. She volunteered for the newly formed Youngspiration party and ran for a seat in a local district council in 2015. She lost, but was spurred to run for the legislature after violent clashes broke out in February.
Her experience in the youth movement slowly transformed a quiet young woman into an outspoken, irreverent young politician. Together with Mr. Leung, she has helped to trigger what may turn into a constitutional crisis, should China’s Parliament move to block them from taking office.
Mr. Leung recalled that when Ms. Yau joined the Youngspiration party in early 2015, she used to keep to herself.
“She didn’t know how to express herself. To be blunt, she was quite a nerd,” he said. “But in the two years since she’s been forced to speak and has changed a lot.”
Ms. Yau’s experience until 2014 offered few clues to suggest she would become so passionate about Hong Kong’s future. Her parents — both retired civil servants — wanted her to work for a few years in her steady job and then, perhaps, go to graduate school. Until 2014, she complied.
But, as Ms. Yau describes it, she could not countenance students — some still in high school — confronting the police on Hong Kong’s streets while she worked at a comfortable desk job just blocks away. “They are too young to bear this kind of social responsibility,” she said. “I had to pay something for this place.”
Some of her experiences as a student suggest that, if anything, she strongly identified with the Chinese nation, if not the Communist government that has run it since 1949.
At Hong Kong’s Lingnan University, Ms. Yau studied Chinese literature. She said she enjoyed writing fictionalized accounts of the romantic intrigue — especially homosexual relations — in China’s imperial dynasties, notably the Qin, the first dynasty that flourished more than 2,200 years ago. As for China’s last dynasty, the Qing, she said she had little interest because its rulers — the Manchus — were foreigners.
“I don’t think it is a real dynasty for Chinese people,” she said.
Even before she attended college, she said she was particularly affected by the Analects, the collection of sayings and ideas attributed to the philosopher Confucius. In some ways, they have helped shape her still developing worldview, particularly her strident anti-Communism.
To Ms. Yau, the government in Beijing has, through its political campaigns, destroyed much that is good about Chinese society. She considers Taiwan, which Beijing holds is a breakaway province, a better guardian of Chinese traditions, and that Chinese President Xi Jinping’s recent emphasis on Confucian values is superficial and not in keeping with the true spirit of the sage.
But even if China abandoned Communism and embraced its thousands of years of history, Ms. Yau said her loyalties lie with Hong Kong, which embarked on a very different path after the British established their colony in the 1840s. She sees Hong Kong’s civil liberties — the same ones that allowed her to protest and then win a seat on the legislature — as being under mortal threat by an ever-intrusive mainland government.
At 25 years old, she has come under intense criticism for her inauguration, during which she laid out a blue banner that read “Hong Kong Is Not China.” Even some of her allies considered her profanity-laced oath childish.
That speaks to the divide between older pro-democracy supporters, who accept Chinese sovereignty, and many in the younger generation, who do not. Emily Lau, the longtime head of Hong Kong’s Democratic Party, said it was unwise of Ms. Yau and Mr. Leung to use the term “Chee-na.”
“I don’t agree with that at all and understand why many people feel infuriated and insulted,” Ms. Lau said, adding that she also strongly disagreed with the pro-Beijing camp’s attempt to prevent the pair from taking office.
Ms. Yau, now in danger of losing her seat, did not want to comment on her oath, citing a court case on whether she will be allowed to retake the pledge. Even so, on Wednesday she and Mr. Leung tried to retake their oaths, unannounced, in a chaotic and aborted legislative session. The body’s president called their action “ridiculous” and asked them to leave.
“We have to protect our own values, our freedoms,” Ms. Yau said. “Some people have to stand up and fight for these kind of things.”