According to South Korea's Consulate General in Hong Kong, Hong Kong police are interrogating the man, who was arrested at around 2 a.m. Sunday at the shopping district of Mong Kok.
But they charged onto the streets after 9:00pm, with hundreds of officers in riot gear pushing back crowds who jeered them.
From morning to late in the evening, we follow her preparing for the protests, marching and later being confronted with riot police and tear gas.
A few days later, the head of the Chinese military garrison condemned protesters and said their actions "should not be tolerated".
The protests in Hong Kong were sparked in June by a proposed law that would have allowed Hong Kong residents to be sent to mainland China to stand trial.
The Hong Kong protesters defied police warnings and went past the designated endpoint for the Saturday's rally in Mong Kok.
"I've never seen anything like this".
However, more anti-government protests are scheduled for Sunday with a mass strike on Monday, as the protestors continue to be angered over the government's refusal to communicate, violent ways of police to put an end to the protests and the arrest of 44 people this week on rioting charges. Authorities said their resources were stretched due to the prolonged demonstrations.
Earlier in the afternoon, some of the anti-government protesters had marched from Mongkok to the cross-harbour tunnel and briefly blocked it to vehicles, amid warnings by police not to obstruct traffic. Many carried hiking sticks and some held homemade shields.
Beijing has increasingly pitched the anti-government protests as funded by the West.
"We don't stay in the same place".
"If the police are too strong, we will leave".
In Washington on Friday, a bipartisan group of United States lawmakers called on the Trump administration to halt future sales of munitions and crowd-control equipment to Hong Kong's police force, which has been accused of using excessive force against protesters.
The park where the pro-police rally was held was filled instead by predominantly older people dressed in white, speaking a range of Chinese dialects.
China has provided little evidence beyond supportive statements from some Western politicians and critics say Beijing's accusations of foreign meddling ignore Hong Kongers' legitimate grievances.
The main entrance of the landmark Peninsula Hotel was closed.
Separately, a smaller pro-police rally was held in another area of the city, which saw demonstrators carrying Chinese flags and chanting messages of support for Hong Kong's beleaguered police department.
The government said late on Sunday that "blatant violation of law, wanton destruction of public peace and violent attacks on the police" harm Hong Kong's society and economic livelihood. "We don't need a so-called "HK revolution", we only need to do our best, which is enough", he told the crowd.
Sylvia Lam, 61, who described herself as a housewife, said she had turned up at the pro-police rally to oppose violence.
"I feel extremely uncomfortable when every time I watch TV, the scenes are so radical", she said. "Young people should stop and think, don't become someone's political tools, be rational please".
The organizer estimated the size of the crowd at the pro-police event as 90,000, while the police said the crowd numbered 26,000 at its peak.
For the past few months, protests in Hong Kong have occurred nearly daily, with many calling this the biggest political crisis in the urban centre's history.
They also pose a major challenge to Chinese leader Xi Jinping who is already grappling with an accelerating trade war with the USA and a slowing economy in a politically-sensitive year.
Months of demonstrations are taking a growing toll on the city's economy, with local shoppers and tourists avoiding parts of one of the world's most famous shopping destinations.
Saturday's march comes after a group of civil servants - ordered to be politically neutral - joined demonstrations in their thousands on Friday.
Former Hong Kong leader C.Y. Leung offered 1 million Hong Kong dollars ($127,720) for information about who threw the flag into the water.