North and South Korean athletes walking together with unification flags depicting the Korean Peninsula during last week’s Opening Ceremonies in PyeongChang. (Kim Kyung-Hoon/Reuters)

BONGPYEONG, South Korea — ­ Over the last few days, South Koreans have watched one of the world’s deepest cross-border freezes begin to thaw. They first saw television footage of a North Korean plane landing outside Seoul. They then saw a ruling Kim family member hopping around the country, attending the PyeongChang Olympics, meeting with South Korean President Moon Jae-in — and getting red carpet treatment. Then they heard news that the North was inviting Moon to Pyongyang for the kind of summit that hasn’t happened in more than a decade.

South Koreans so far have welcomed the most immediate result of those rapid diplomatic developments: a Winter Olympics free of threat from the North. But many here — particularly in younger generations — are also deeply skeptical of the broader inter-Korean effort, wary of North Korea’s intentions and concerned about the whopping economic burden that would come with unification.

That’s led to a different kind of fraught moment on the peninsula — one in which the South is again cooperating with the government in Pyongyang even as its people are less certain than ever about the path they want. In interviews at Olympic venues over the last several days, Koreans say they have been mesmerized by the diplomatic spectacle — particularly the visit of Kim Jong Un’s sister, Kim Yo Jong — but some suggested that the South’s welcoming stance was unearned or overdone.

“It was a strange feeling seeing North Koreans in South Korean territory,” said Shin Hye-mi, 36, near a snowboarding venue. “At some points, I thought we were doing too much for them.”

“We don’t need unification with North Korea, so I hope we don’t try to make it happen,” said Chung Seok-ho, 39. “We have too much to lose from unifying with North Korea, and so many things are on the line. It’ll be much better for us to just be two separate systems existing side by side.”

Moon himself remains popular in South Korea, though, and young people say they are willing to put some faith in a leader who came into office last year after months of street protests against his predecessor, Park Geun-hye.

“I support President Moon, and I believe he’s doing a great job,” said Joo Sang-ha, 34, from Seoul. “Kim Jong Un’s summit proposal signifies that he is acknowledging President Moon as his counterpart, unlike he did with previous administrations. So it’s a good sign for better relations with North Korea.”

During these Olympics, the two Koreas have been cooperating like no time in the last decade. First, they agreed to field a unified women’s hockey team and march together during the Opening Ceremonies under a unified flag — a light blue silhouette of the peninsula. Then, last weekend, Kim Yo Jong became a constant and smiling presence on South Korean television — spotted attending a hockey game, going to the South’s presidential palace, signing a Blue House guest book wishing for prosperity and unification.

Skepticism about what has happened during these Olympics comes from the fear that North Korea is being opportunistic — grabbing the world’s attention without any intent to change its behavior.

“North Korea has always been talking peace but has been developing and provoking with its nuclear weapons and missiles,” said Jeong Min-ho, a 21-year-old college student attending the Olympics. “So I don’t see how the situation can take a positive turn after the Olympics.”

Moon, who took office last year, is a progressive who has advocated for closer ties with the North, nudging South Korea back toward what it once called the Sunshine Policy. During that period, roughly from 1998 to 2008, South Korean presidents held two summits with then-North Korean leader Kim Jong Il, all while giving the authoritarian country large shipments of aid. The hope was that warmer ties — and a growing economy — could prompt the North to scale down its weapons program. Instead, the North built up its nuclear stockpile and has tested six weapons since 2006.

Meanwhile, there has been a pronounced shift in attitudes in the South. Unlike their parents and grandparents, younger South Koreans don’t see unification as a clear national goal — despite a national education curriculum that presents it as such. Instead, they worry about what will happen to their own standards of living if the South is suddenly tethered to one of the world’s economic weaklings. By some estimates, unification could cost $1 trillion.

The Winter Olympics in PyeongChang, South Korea are happening miles from the tense border with North Korea. The boundary has soldiers on edge, and nearby residents worried. (Lee Powell/The Washington Post)

According to a December 2017 survey conducted by the Korea Institute for National Unification, a government-funded think tank in Seoul, 14 percent of South Koreans in their 20s said they wished for unification. That number rose to 63 percent for people in their 50s and 60s.

Still, for some, the incentives for closer ties run deep. Some South Koreans still have family members across the border. Others believe that shared Korean blood is reason enough to do away with the divisions. Still others talk about practical reasons: If North and South Korea unified peacefully, Asia’s greatest security problem would disappear.

“I think the North Korean visit here can be a very good chance for South Korea,” said Kwon Soonson, 43, a software programmer who was planning to watch moguls skiing. “Kim Jong Un sending his own sister to South Korea is a very rare occasion, so we should grab that chance. Until very recently, the U.S. and North Korea were literally on the verge of war. But now we are seeing quite a different setting.”

Especially during the last 10 years, under more conservative presidents, a near-impermeable seal has existed between the two Koreas. A train line designed to cross the Demilitarized Zone doesn’t run. South Koreans can’t send mail to the North or call.

“It’s great to have the North Korean officials here because otherwise, the whole Olympics could have been just about the dangers of being in South Korea,” said Kim Tae-woo, 34, who works at a forklift manufacturing company in Seoul. “I like the North Koreans coming to South Korea because it’s assurance of safety for now. Of course, everything can all go back to the tense times after the Games. We’ve had similar experiences with North Korea in the past. Even if it is temporary peace, it’s better than nothing.”