HONG KONG — The suspect in a murder case that led indirectly to the ongoing protests in Hong Kong was released from prison on Wednesday and said he would surrender himself to Taiwan, where he is wanted for killing his girlfriend during a Valentine’s Day trip last year.

The suspect, Chan Tong-kai, who had been serving a sentence for money laundering, walked out of Pik Uk Prison in Hong Kong and said he wanted to apologize to his girlfriend’s family for the “irreversible mistakes” he had committed. He thanked his family for standing by him.

But Mr. Chan’s case — like Hong Kong’s political crisis, which began with protests against an extradition bill meant to ensure his prosecution on murder charges in Taiwan — is far from being resolved.

Though Mr. Chan has said he would surrender to Taiwan, that self-governing island and Hong Kong are arguing over the terms. The disagreement is rooted in Taiwan’s disputed sovereignty.

China claims Taiwan is part of its territory, and Hong Kong, a semiautonomous region of China, is wary of any arrangement that would seem to confer recognition on Taiwan’s government. Taiwanese officials, for their part, have complained about a lack of cooperation from Hong Kong, and they have questioned whether they would receive enough assistance from the city’s authorities to successfully prosecute Mr. Chan.

“According to the Hong Kong side, if we make a request for evidence with regards to Chan’s surrender, the Hong Kong side will actively cooperate. But it also said there is no law for cooperating with Taiwan on criminal justice,” Taiwan’s Mainland Affairs Council said in a statement on Sunday. “We plan to ask the Hong Kong government, based on this contradictory statement, how can you provide assistance to us?”

Hong Kong officials say such reservations risk undermining the opportunity to prosecute Mr. Chan. The city’s No. 2 official, Chief Secretary Matthew Cheung, on Tuesday urged Taiwan not to “complicate a simple issue” or “try to exploit politics in order to achieve certain gain at the expense, particularly, of justice.”

Mr. Chan, 20, a Hong Kong resident, was sentenced in April to 29 months in prison for money laundering over possession of valuables that had belonged to his girlfriend, Poon Hiu-wing, also from Hong Kong. He had traveled with her to Taiwan in February 2018, but returned alone.

Mr. Chan later told the Hong Kong police that he had strangled Ms. Poon, put her body in a suitcase and hid it in some bushes. Investigators found her body near a subway station in northern Taiwan.

The Hong Kong authorities said they could not prosecute Mr. Chan for murder in Hong Kong, and that the lack of an extradition agreement with Taiwan meant he could not be sent there.

In February, the Hong Kong government proposed legislation that would allow rendition to places with which it does not have such an agreement. The bill incited widespread suspicion and enormous protests because it would have also allowed extraditions to mainland China, where the legal system is far less transparent than Hong Kong’s and is controlled by the Communist Party.

Hong Kong’s leader, Chief Executive Carrie Lam, said last month that she would formally withdraw the bill. But protests have continued over other demands, including an investigation into the use of force by the police, amnesty for arrested protesters and direct elections.

Mr. Chan was released on Wednesday because his sentence was reduced for good behavior. He left the prison in a van, accompanied by a clergyman who had met with him during his incarceration.

President Tsai Ing-wen of Taiwan said Tuesday that she hoped Hong Kong would look for ways to prosecute Mr. Chan itself, or provide all necessary evidence and cooperation if he were sent to Taiwan.

“Hong Kong people travel all over, go to every country around the world,” Ms. Tsai said while campaigning for re-election on Tuesday. “If things happen in other countries and the Hong Kong government takes this attitude, then this will cause headaches and those governments will feel the Hong Kong government is not very responsible.”

Han Kuo-yu, the presidential candidate of Taiwan’s opposition party, the Kuomintang, criticized the stance of Ms. Tsai’s government, saying the result would be “too horrible to contemplate” if he were not allowed to surrender to the Taiwan authorities.

Any person from a country that Taiwan does not have an extradition agreement with could “come to Taiwan, kill people, light fires and run away,” Mr. Han said. “Does this mean it is all fine?”

Early Wednesday, Taiwan’s Mainland Affairs Council said it had asked to send officers to Hong Kong to escort Mr. Chan. But the Hong Kong government said it saw that request as “cross-jurisdiction law enforcement, which is a disrespect for Hong Kong’s jurisdictional power and is totally unacceptable.”

James To, a Hong Kong lawmaker who recently visited Taiwan for informal discussions about the case, said on Tuesday that Taiwan officials had reason to be suspicious.

“If you step in the shoes of Taiwan authorities, Hong Kong police have not cooperated with them, they have not delivered any evidence to them, has not informed them of your investigation and detailed evidence gathered through Hong Kong operations,” he said. “How can the other side, the Taiwan side, trust you?

Ezra Cheung contributed reporting.