When Hong Kong hosted Lebanon in a recent soccer match, several hundred young home fans erupted in a chorus of boos shortly before kick-off, turning their backs to the pitch and raising their middle fingers. They were not jeering the opposition but their own national anthem -- China's "March of the Volunteers."
This protest has become a mainstay of Hong Kong international matches since the Occupy movement of 2014, when tens of thousands of mostly young Hong Kongers took to the streets in a forlorn effort to pressure Beijing to let the semi-autonomous city elect its own leader.
Viewed in isolation, the antics of a few soccer fans have little significance for the rest of Asia. But the deep frustration felt by young Hong Kongers toward China's ruling Communist Party -- and Beijing's increasingly tough response -- are a potent warning of the frictions ahead as an emboldened President Xi Jinping looks to stamp China's authority on the region.
To put an end to the booing, Beijing recently passed a new national anthem law. Hong Kong must now implement local legislation to enforce the criminalization of disrespect for the song.
SUSTAINED PRESSURE Coming amid the flurry of legal and extralegal interventions in Hong Kong over the last couple of years, Beijing is sending a message to the 7.4 million people of this querulous city that the rules of the game are changing.
Numerous officials have stated that the "high degree of autonomy" and civic freedoms promised to Hong Kong for 50 years after the handover are not so much inalienable rights as privileges that will only be extended if not used to challenge Beijing.
With so much opposition in Hong Kong, then, it is little wonder that the city's unique freedoms are under sustained pressure.
Elected local lawmakers have been ousted at the behest of China's rubber-stamp parliament. The once vibrant publishing industry has been shaken by the kidnapping of booksellers who attacked the Communist leadership. Critical activists and academics from overseas have been denied entry to Hong Kong, as part of a wider campaign to squelch opposition.
Beijing is partly responding to the defiance of a post-handover generation that fears the growing threat to its identity and way of life, as I explain in my new book, "Generation HK: Seeking Identity in China's Shadow."
But the tensions gripping this metropolis are as much about China as they are about Hong Kong.
That is why a senior Southeast Asian official told me recently that the region should pay more attention to what is happening in the city. "Hong Kong feels the pressure first as it's closest to Beijing and it's officially part of China," he said. "But the squeeze will hit us all."
There are three main reasons why the rest of Asia should be concerned.
Firstly, the tightening of control over Hong Kong is evidence of a Chinese government that is much stronger, more self-confident and no longer willing to stick to former leader Deng Xiaoping's exhortation to "hide your strength, bide your time."
That more muscular vision is embodied by President Xi, who has amassed more personal power than any Chinese leader since Mao Zedong.
After the handover from British rule in 1997, many Hong Kongers hoped that as China's economy grew, the country would open up politically over time and that they could help accelerate the process.
Many in the Western world bought into a similar assumption about the benefits of engagement with China. But, as advisers to U.S. President Donald Trump noted in the White House's new National Security Strategy, China was not compliant.
"For decades, U.S. policy was rooted in the belief that support for China's rise and for its integration into the post-war international order would liberalize China," they wrote. "Contrary to our hopes, China expanded its power at the expense of the sovereignty of others."
Secondly, China's failure to win the hearts and minds of Hong Kongers, most of whom share ethnicity, language, culture and familial ties with the mainland, suggests that Beijing's wider quest to promote soft power in the rest of Asia and beyond will be difficult indeed.
A long-running survey by the polling center at the University of Hong Kong shows that the proportion of young Hong Kongers who describe their ethnic identity as "broadly Chinese" has dropped from 32% just after the handover to a low of 3%, while the proportion who describe their identity as "Hong Konger" has surged from 68% to 94%.
Many of the young Hong Kongers I interviewed for my book accept, of course, that they are of Chinese origin. However, they are rejecting a Chinese identity that has been co-opted by the Communist Party. And they are rejecting Beijing's efforts to enforce its values and way of thinking on the city.
As Beijing's "with us or against us" mentality intensifies, it will deepen fault lines beyond China and Hong Kong. Even countries with reasonably friendly business and cultural relations with China such as Singapore and South Korea have been put under pressure by Beijing over their military ties with Taiwan and the U.S., respectively.
PERCEPTION GAP Thirdly, the vast perception gap between Beijing and many Hong Kongers mirrors the misunderstandings that have exacerbated tensions between China and much of Asia.
Over my seven years reporting in Southeast Asia, countless local diplomats and politicians complained about China's growing assertiveness in the South China Sea and beyond.
It was only when I moved to China in 2015 that I heard the other side of the story more fully. Despite the power mismatch, Chinese officials and academics felt it was their country that had been bullied and taken advantage of, as several Southeast Asian nations ganged up with the U.S. and Japan.
Similarly, in Hong Kong, Chinese officials seem bewildered by what has happened. Rather than analyze their own missteps, they blame Hong Kongers for exploiting China's goodwill and relative weakness after the handover and the British colonialists for implanting Western ideals of democracy and free speech.
The wide gulf between Beijing and young Hong Kongers bodes ill for the city's future. The divisions are deepening further, with the prosecution and jailing of a growing number of democracy activists.
As the battle intensifies, it is easy for the rest of Asia to look away from what is, in legal terms, an internal Chinese matter.
But Beijing's treatment of Hong Kong should concern all those who care about how China's rise will reshape the region -- and the world.
Ben Bland is the author of "Generation HK: Seeking Identity in China's Shadow" and the South China correspondent for the Financial Times.