Kim Jong Un and North Korea's top brass will have a less hawkish leader to deal with compared to Park, and there are reasons for Pyongyang to be both happy and concerned about it.

"North Koreans I spoke to were very excited at the prospect of a liberal government in the Blue House here in South Korea," said Jean Lee, a senior fellow at the Wilson Center who was in Pyongyang last week. "(Moon's election) will definitely mean a change in regional politics when it comes to North Korea."

But North Korea is used to international pressure and isolation. To a certain extent, it's an advantage.

"I don't think they're popping the champagne bottles because there's a whole set of difficulties that come with North Korea being engaged. In some ways it's a bigger stress on their system. They're very good at dealing with hostility and they know how to be isolated. It's harder for their system to have dialogue and cooperation," said John Delury, a professor at Yonsei University's Graduate School of International Relations.

North Korea's Kim has only dealt with conservatives in South Korea since taking power in 2011. Facing a more approachable adversary will be different.

It also may help North Korea get a seat at the negotiating table, something US Secretary of State Rex Tillerson said could happen only when "conditions are right."

Moon was an integral part of the "Sunshine Policy" of increased engagement with North Korea while he served as former President Roh Moo-hyun's chief of staff.

That could mean expanding operations at the jointly run Kaesong Industrial Complex and sending more investment across the border.

But more engagement could drive a wedge between Seoul and Washington, which has taken a tough line on North Korea since President Donald Trump's inauguration.

"It's a different time. North Korea has made a lot of progress on their nuclear and missile programs, so it's a different type of threat," said Daniel Pinkston, a lecturer in international relations at Troy University in Seoul.

The shift in US-South Korea relations could also bode poorly for North Korea. Moon is still likely beholden to Trump's policy to a certain extent -- which is ramping up pressure on Pyongyang to drive officials there to the negotiating table.

That strategy could get in the way of Moon's proposals.

"North Koreans are pretty strict about dealing with the nuclear issue in the context of their relationship with the United States, and so that of course is one of the big challenges for Moon because he's going to want to improve inter-Korean relations but he doesn't have much leverage on the nuclear issue," said Yonsei University's Delury.

Moon's been clear about the importance of the US-South Korean alliance. But he's said South Korea shouldn't be afraid to say no to the US.

"The problem of resolving of issues in Korean Peninsula should be led by South Korea and helped by our neighboring countries such as the United States, which is our leading ally," Moon said in a campaign video.

Those shared concerns could draw China -- North Korea's most important international patron -- and South Korea closer together, analysts say.

Moon said he'd be willing to negotiate with both China and the US regarding THAAD, short for the Terminal High Altitude Area Defense system.

"To resolve the issue with THAAD, we will earnestly negotiate with the US and China. Strong security comes from strong military strength," he said.

China has continued to call for dialogue to stabilize the situation on the Korean Peninsula and views the THAAD deployment with hostility.

Though there's a concern that THAAD could up the ante in an arms race, Beijing's concerns largely have to do with the missile-defense system's powerful radar, which could be used to monitor activity inside China, experts say.

"This has hurt South Korea at a time when the economy has moved into a slow-growth phase," Pinkston said. "Moon will be under pressure to address these issues."