PYEONGCHANG, South Korea — It was a moment that was unimaginable on Monday. But on Friday, it was reality.

The South Korean president, Moon Jae-in, shaking hands with a member of North Korean royalty, “First Sister” Kim Yo Jong. Both of them with smiles on their faces. Both of them speaking their shared language.

Both of them making a point to the outside world.

Moon wanted to use the Winter Olympics in PyeongChang as a way to engage with North Korea, to show the world — and the United States in particular — that old-fashioned diplomacy still has a role to play, even with Kim Jong Un's belligerent regime.

And for her part, Kim Yo Jong, the North Korean leader's younger sister, seemed to be saying: See, we're not that scary. We can cooperate with those who aren't threatening to rain “fire and fury” down upon us.

The photo of Moon and Kim Yo Jong in animated greeting quickly went viral in South Korea, a glimmer of what could be.

Because of the tiered seating, Moon is standing below Kim — which means he is literally looking up to her. In terms of both diplomatic protocol and Korean custom, that’s a win for Kim.

Kim was attending the Opening Ceremonies together with Kim Yong Nam, who is 90 years old and is technically North Korea's head of state, although all power rests with the “great leader” Kim Jong Un. Their attendance came as something of a last-minute surprise, the result of a rapidly unfolding series of events that began Jan. 1. Kim delivered a New Year's Day address offering “detente” and setting in motion the chain of events that led to the isolated nation sending about 500 North Koreans, including 22 athletes, to the Olympics.

But it was Kim Yo Jong who is the object of most South Korean fascination. She is the first member of North Korea's ruling Kim family to travel to South Korea. At about 30 years, old she is young and clearly has her brother's trust.

South Korean television networks broadcast live coverage of the North Korean jet's arrival at the Incheon airport, west of Seoul, on Friday afternoon. From then on, cameras documented Kim's every gesture and her every move.

They caught her wide, relaxed smile when she gestured to Kim Yong Nam to take the most senior seat in a meeting room at the airport when they sat down with South Korean officials.

They documented her transfer to the new high-speed train — complete with super-fast WiFi, of course — connecting the airport and the Olympics site. And they were waiting when she disembarked at Jinbu station, surrounded by the kind of paparazzi throng and security detail that are usually the preserve of K-pop stars.

At the Opening Ceremonies of the Olympics on Feb. 9, Vice President Pence was seated near Kim Yo Jong, North Korean leader Kim Jong Un’s younger sister.

Kim Yo Jong didn't attend the reception for VIPs before the Opening Ceremonies, but she was in the VIP box for the big event, dressed in a black coat and hat. It was the kind of no-frills, I-mean-business attire that she wears in North Korea, where she works for her brother. Her ID badge around her neck showed the official photo of her that was released last year when she was elevated to North Korea's powerful Politburo.

She happily accepted Moon's warm greeting, and she stood and clapped when the unified Korean team entered the stadium.

If North Korea sees this as a charm offensive, it could hardly have picked a better ambassador.

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