Transcript for Oscar-nominated documentary looks inside Hong Kong's pro-democracy struggle
We can never take freedom for granted. Reporter: Jo is Yu knows what she's talking about. Yes, they just fired tear gas. Reporter: She's one of the many faces of Hong Kong's fight for freedom against communist China's authority. I think it is very clear that even the very civilized or very developed city like Hong Kong could be turned into like the other cities in mainland China, that is, without freedom, without basic human rights, also without democracy. Reporter: It's a dire warning to the rest of the world from a woman who took to the streets for months, protesting for her homeland. Why did you feel strongly enough to join the pro-democracy movement? I have always been very passionate, keen on understanding social issues. I never expected myself to participate in a very large social movement as a student leader or student activist. Reporter: The 22-year-old college student was thrust into the revolution by chance, propelled by a sense of responsibility and obligation. Very naturally, I just got engaged in like all these organizations and all these -- organizing of like grassroot protests, demonstrations, rallies and everything. Reporter: Joey's sacrifice and determination captured in the new Oscar nominated documentary "Do not split." Centering around the Hong Kong demonstrations two years ago. Beijing put so much pressure on Hong Kong in order to reshape Hong Kong in their picture. Reporter: 2019 was a year of global unrest, protests in Hong Kong spurring demonstrations across the world. The former British colony handed over to China in 1997. For the most part enjoyed some form of Independence from the mainland. But over time the city's rights slowly eroded. In 2019, a bill was introduced that would allow criminal suspects to be extradited to mainland China, sparking massive unrest. The proposed law seen as an attack on Hong Kong's human rights. Even after the bill was shelved, the protests raged on. It is not only just about any single legislation or policy that is going to be passed in Hong Kong, it is really about the continuous and also long-term encroachment and also crackdown from the communist party. Reporter: Over the course of a new, director anders hammer followed the Hong Kong protesters. The biggest impact was to see these young protesters going through this great trauma about losing basically their security as they knew it. What was it like when the tear gas started hitting and it became increasingly more militarized? To be honest, it was really terrifying. Every day when we take to the streets, when we participate in demonstrations and protests, we don't even know whether we can safely return home. China is not known for reacting in a peaceful manner if they feel that their main political aims are being threatened. Reporter: That's exactly why anders wasn't surprised when Hong Kong's largest broadcaster, partly owned by a pro-beijing contort up, dropped the oscars telecast after more than 50 years of airing the ceremony. The network called it a purely commercial decision. But some reports say "Do not split's" nomination played a large role in the apparent censorship. In this censorship, our documentary has become a part of the story. It's actually a signal showing us that Hong Kong is really gradually becoming another mainland city. And that is really, really depressing. Reporter: Joey was born in North Carolina, raised by her grandparents, later immigrating to Hong Kong at age 7. They have always wanted me to be obedient, to be a good girl, and then to have -- to live a very ordinary but then successful life. Now obviously I have, like, exceeded the expectations and did not live the life that they wanted me to live. Reporter: Her lifelong dream was to become a teacher, a dream she had to cast aside when she joined the uprising. Did you feel like you had to sacrifice your future in order to lead this movement? What we were really thinking about is actually the future of Hong Kong instead of the future of our own. So I don't see that as a very large sacrifice. Because I know that there are a lot more others who are making larger sacrifices than I do. Reporter: And while the pandemic had largely paused mass demonstrations -- thousands of activists later charged back into the streets, reigniting calls for democracy. To quell the unrest, China stepped in to impose the controversial national security law, making it easier to punish protesters. Joey, fearful she could be charged under the new law, into exile, fleeing to Washington, D.C., determined to sustain the pro-democracy movement from afar. You know people who were arrested under the new law? Some of them are close friends of mine. And that was really traumatizing and disheartening. Almost every prominent pro-democracy leaders of Hong Kong have either been arrested, imprisoned, or forced into exile right now. For now, there is actually no room left for the people who are still inside of Hong Kong to exercise their rights to participate in demonstrations or to enjoy the freedom of expressing themselves, of expressing their political opinions. What is the future for the movement now? We have also got a lot of Hong kongers overseas who are establishing different Hong Kong diaspora communities who are trying to advocate for different legislations that protect and also defends others of Hong Reporter: For now, Joey hopes "Do not split" resonates with viewers who could carry on the battle for democracy in their own corners of the world. This is not only a fight between the people of Hong Kong to the Chinese communist party, this is actually a fight between all the freedom lovers against any tyrannies across the globe. And a programming note, here in the U.S. You can watch the oscars this Sunday evening, 8:00/7:00 central here on ABC.
This transcript has been automatically generated and may not be 100% accurate.