Months of increasingly violent pro-democracy demonstrations in the financial hub were sparked by protests against a now-cancelled extradition law -- which would have allowed suspects to be extradited to the authoritarian mainland China.
Hong Konger Chan Tong-kai, 20, is wanted in Taiwan for the 2018 murder of his pregnant girlfriend Poon Hiu-wing.
Chan, who spent 18 months in custody over money laundering charges, apologised to the victim's family and the city as he left the maximum security prison.
He apologised for the great "pain and agony" he had caused Poon's family, and hoped his decision to surrender would offer them some relief.
"As for the society and Hong Kongers, I could only (say) I'm sorry," he said, adding that he hoped to be forgiven and start life afresh.
Chan, ignoring reporters' other questions, said: "I am willing to surrender myself... and go back to Taiwan to face the trial and serve the sentence."
However, Chan will not leave Hong Kong for Taiwan yet.
Taiwanese authorities said in a press conference that he would not be admitted to the self-ruled island like ordinary visitors, according to reverend Peter Koon, who frequently visited Chan in prison.
"Our original plan was that I would accompany him to Taiwan and (the press) wouldn't have seen him," Koon told AFP, adding that Chan would have been sent directly from the prison to the city's airport.
Taiwan had said it asked to collect Chan -- and the relevant evidence -- but was rejected by Hong Kong authorities, who called the request disrespectful and "totally unacceptable".
The city has seen the worst unrest since the city's handover from Britain, as the movement sparked by opposition to the extraction bill seeks greater democracy and police accountability.