SEOUL—North Korea is stealing the thunder, if not the show, from the Americans at the Pyeongchang Olympics, with word that the charming younger sister of ruler Kim Jong Un is arriving Friday for an Opening Ceremony that will also feature U.S. Vice President Mike Pence.

South Korea’s unification ministry had no sooner announced that 28-year-old Kim Yo Jong would be along for the ride than Pence, in Tokyo, was saying the U.S. would soon announce “the toughest, most aggressive round of economic sanctions ever” on North Korea.

No question, the excitement generated by news of the younger sister’s presence eclipsed what essentially seemed like the same old boring story—more sanctions of questionable value in persuading Kim Jong Un to abandon his nuclear program. Rather than attempt to undermine the Olympics by missile shots, much less threats of terrorism, older brother Kim has resorted to the ultimate weapon in his charm offensive in the form of the lovely Kim Yo Jong, known in both North and South Korea for smiling prettily while saying very little on North Korean TV.

In fact, she undoubtedly is a power in her own right, thanks to her title of first vice director of the propaganda and agitation director of the ruling Workers’ Party, but she’s not expected to deliver any policy declarations, much less hint at negotiations on the North’s nuclear program.

The real question is whether she and Pence will shake hands while both are watching the Opening Ceremony from the heated confines of a VIP center, while the crowds in the stands down below shiver in the coldest-ever Winter Olympics. She’ll presumably be right beside North Korea’s ceremonial head of state, 90-year-old Kim Yong Nam, leading the official delegation, plus 140 musicians and entertainers and more than 200 “cheerleaders” who arrived Wednesday wearing crimson dresses and fur hats.

They’re here ostensibly just to cheer on the North’s 22 athletes, marching with South Koreans in the opening under the one-Korea flag, a light blue image of the Korean Peninsula against a white field, but Kim Yo Jong’s presence signifies much more.

It’s the first time ever that any member of North Korea’s Kim dynasty, beginning with grandfather Kim Il Sung, who ruled for nearly 50 years, has been to South Korea, and she’s sure to become a luminary in the South Korean media.

As for Pence, his pugnacious words, as he met with Japan’s Prime Minister Shinzo Abe, seem distinctly out of sync with the tenor of little sister’s visit and the whole show the North Koreans are putting on in a bid to win hearts and minds in South Korea.

While Koreans were salivating over the prospect of seeing Kim Yo Jong, Pence in Tokyo was talking darkly of the need for North Korea to “once and for all abandon its nuclear weapons program and ballistic missile ambitions.”

His menacing words, along with the vow to work with America’s allies to “achieve the global objective of denuclearization of the Korean Peninsula,” definitely seemed out of sync with the mood engendered by the prospect of the opening of the Games and South Korean President Moon Jae-in’s hope that they will be a watershed event on the way to North-South dialogue and reconciliation.

Moon himself was carefully silent about both the U.S. position and North Korea’s campaign to win the confidence of Koreans, but he and Pence presumably will be talking about joint South Korean-U.S. military exercises that have been postponed until after both the Olympics and the ensuing Paralympic Games.

Americans are confident the exercises—annual war games that always inspire torrents of rhetoric from North Korea—will go on as planned, but South Koreans are not so sure. “No one knows,” said one official. “We have to wait and see.”

One possibility is that they may be reduced in size and scope—perhaps without simulated bombing runs by B1 bombers based in Guam that have flown periodically just below the North-South line in an obvious effort to intimidate the North Koreans.

Pence’s tough words put Moon Jae-in in an extremely difficult position as he walks a tightrope between leftists and liberals demanding a breakthrough with North Korea and rightists calling for a “pre-emptive strike” on the North’s missile and nuclear facilities.

Although leftists and liberals elected Moon by a wide majority in a snap election last May after the ouster and jailing of the conservative Park Geun-hye, rightists still exercise considerable power and influence.

They have been embarrassing the government at every chance in the run-up to the Games, shouting slogans and waving South Korean and American flags, vowing to ambush the North Koreans with tirades over mega loudspeakers whenever they show up at athletic contests or cultural exhibitions.

They were out in such force as the North Korean entertainers arrived by boat at a port on the east coast that the North Koreans refused to get off.