The martial law decree and the six months of ensuing turmoil saw three different acting presidents and multiple criminal insurrection trials for Yoon and several top officials.

It marked a stunning political self-destruction for the former leader and effectively handed the presidency to his main rival.

"I was here on December 3 after martial was declared and December 14 when Yoon was impeached," said Choi Mi-jeong, 55, a science teacher. "Now Lee Jae-myung is becoming president. I hope he will become a leader who supports ordinary people, not vested interests, not a small number of riches."

Official results were expected to be certified by the National Election Commission on Wednesday morning.

We're wrapping up our live coverage but you can follow the latest developments from our colleagues here.

South Koreans voted in Lee Jae-myung as their next president in the country's June 3 snap election to heal the wounds of a shock martial law declaration in December.

But the liberal leader comes with his own legal baggage in the form of five different criminal trials.

Democratic Party leader Lee has denied wrongdoing and while a president has immunity from most crimes, legal experts are unclear whether this applies to cases that started before they took office.

ELECTION LAW

South Korea's Supreme Court ruled in May that Lee had violated election law by publicly making "false statements" during his 2022 presidential bid, and sent the case back to an appeals court after overturning an earlier ruling clearing him.

The Seoul High Court decided to schedule its reconsideration of the case for June 18, pushing back a ruling that could determine his eligibility to run until after the election.

Violation of election law had been in the spotlight because if the appeals court finalises a guilty verdict in line with the Supreme Court's decision, Lee would be barred from contesting elections for at least five years.

Lee will take office with a resounding mandate and his Democratic Party in control of parliament.

Healing the political rifts that led to former President Yoon Suk Yeol's shock martial law and its divisive aftermath will be a tall order.

While Lee has had his eye on the presidency for years, there have been major developments since he narrowly lost to Yoon in the 2022 election, said Kim Jun-seok, a political science professor at Dongguk University.

"Now he has restoration of democracy as one of his tasks," Kim said. "Nonetheless, there are huge challenges faced by South Korea. A grim outlook on the economy that's projected to grow maybe less than 1%. And there's a crisis outside, dealing with Trump. He has a lot of work to do."

Lee has pledged to draft a second supplementary budget for the year as soon as the election is over, and promised vouchers to help local businesses and subsidies for childcare, youth, and the elderly to address growing discontent around tightening purse strings.

His camp says they intend to seek more time to negotiate on trade with U.S. President Donald Trump, but it is unclear how any request for an extension of the tariff deadline will be received in Washington.

With a rise in anti-China sentiment among South Koreans and Trump's push to isolate Beijing, Lee must also tread carefully with any plans to improve ties with China.

The new South Korean administration will likely make efforts to buy time for U.S. trade talks, as it studies the negotiations of bigger neighbors Japan and China for leverage, according to sources familiar with the ruling party's thinking.

President Lee Jae-myung, who is due to take office hours after winning the June 3 snap presidential election without a usual two-month transition period, said on the eve of the elections that "the most pressing matter is trade negotiations with the United States."

The future of South Korea's export-oriented economy will hinge on what kind of deal Lee can strike, with all of his country's key sectors from chips to autos and shipbuilding heavily exposed to global trade.

"I humbly accept the will of the people. I extend my congratulations to candidate Lee Jae-myung. I will never forget the overwhelming support and encouragement the people have given me," said Kim in his concession speech at the party's headquarter in Seoul.

Lee's election win is a result that could reorient a major U.S. ally on policies ranging from China to nuclear weapons and North Korea. 

Former President Yoon had gone all-in on supporting Washington, taking a hard line on North Korea, and repairing ties with Japan. 

Lee, who narrowly lost to Yoon in the 2022 election, has long taken a more skeptical view of the U.S. alliance and vowed to engage with North Korea. He was bitterly critical of Yoon's rapprochement with Japan. 

He made waves on the campaign trail by saying South Korea should keep its distance from any China-Taiwan conflict, later insisting he is not pro-Beijing. 

Tacking toward the center in an effort to win moderates, however, Lee has taken to praising the U.S. alliance.  

He also said he would continue trilateral cooperation with Japan and the United States, seen in Washington as pivotal to countering China and North Korea. 

Some in Washington wonder if Lee's pivot on a range of issues will last, and how his views might clash with Trump.