For Moon Jae-in, the day started well.

There were flowers from well-wishers as he left home and bows from office workers as his motorcade wove through downtown Seoul. He stuck his head out the limousine's sunroof and waved back.

After being elected Tuesday night, he'd normally have weeks to prepare for his new job as president of South Korea. Instead, he was sworn in Wednesday, just a couple of hours after the country's election commission confirmed his victory.

These are not normal times.

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Moon greets his supporters and neighbours as he leaves his house in Seoul. He was sworn in just hours after his election victory was officially confirmed. (Kim Kyung-Hoon/Reuters)

For one thing, the vote was the end of a rushed campaign made necessary by the impeachment and removal of his predecessor, Park Geun-hye. She now sits in a tiny jail cell with a mattress on the floor and waits for trial on charges of bribery and abuse of power.

Then there's the problem next door, the threat of nuclear war.

'Rain fire from the sky'

South Koreans are used to bellicose statements from North Korea and its leader, Kim Jong-un, including vows to "rain fire from the sky" and "lay waste to your towers of steel," even the occasional missile test or underground explosion.

But recently, the threats seem much more plausible. North Korea is getting closer to a working nuclear missile and the United States says it's considering a pre-emptive military strike. Its warships are standing by.

Moon, on the other hand, is offering sunshine.

Sunshine 2.0, to be exact.

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Many experts doubt North Korean leader Kim Jong-un shares Moon's priority of establishing a better relationship between the Koreas. (Reuters)

He plans to revive a policy of engagement with North Korea that was last tried in the 2000s. Moon himself organized the last summit between leaders of the two Koreas in 2007, which featured his mentor, Roh Moo-hyun, and Kim's father, Kim Jong-il.

South Korea showered the North with economic and humanitarian aid. But the nuclear missile program continued and even made impressive gains.

As Moon was sworn in today, he vowed to try again, as he had promised he would during the campaign.

"I will quickly move to solve the crisis in national security," he said optimistically. "I am willing to go anywhere for the peace of the Korean Peninsula — if needed, I will fly immediately to Washington. I will go to Beijing and I will go to Tokyo.

"If the conditions shape up, I will go to Pyongyang."

There don't seem to be any immediate invitations from North Korea.

Kim's goal

During the campaign, Moon said he would need assurances Kim is willing to put his weapons program on hold before talks or joint economic projects could begin. So far, there is no sign of that. In fact, Pyongyang has not yet officially reacted to Moon's election in any way.

For North Korea experts in Seoul, that's not surprising.

Park Byung Kwang of the Institute for National Security Strategy says he can understand that Moon and his supporters have a dream, "however, real politics and real circumstances are different."

"Kim Jong-un's first goal isn't to have a good relationship with South Korea, or to please it," he said. "His goal is to complete the development of nuclear weapons."

In fact, he and other observers here expect Kim to carry out a major test very soon, possibly an underground nuclear explosion. This would be in defiance of threats from both the U.S. and China that such an action could provoke a major reaction from them. And it probably will.

Kim seemed ready to stage such a test weeks ago, but then held back. Observers say it's quite possible he didn't want to influence the South Korean election by scaring voters into choosing a hardliner. They say Moon is more convenient for Kim because he may cause a split between South Korea and the U.S.

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A military parade in Pyongyang back in April marks the 105th birth anniversary of the country's founding father, Kim Il-sung. Many of Moon's supporters hope and believe he can make reconciliation with North Korea a reality. (Damir Sagolj/Reuters)

Washington will put pressure on Moon to harden his stance. But he also faces pressure from the millions of voters who elected him, in many cases hoping and believing that reconciliation with North Korea is possible.

"I very much appreciate that he doesn't consider them our enemy," said Lee Il-young, 34, at a Moon rally in Seoul last weekend. "Moon has the experience to achieve this. North Korea is not an enemy but our partner in the road to peaceful unification."

Unless Pyongyang also sees it that way, Moon's new sunshine project could end up achieving no more than the first one, while giving Kim more time and money to finish his weapons program.