Always flanked by thick groups of bodyguards, Kim Yo Jong commanded attention wherever she went, walking among throngs of journalists with a quiet poise and occasionally shooting an enigmatic smile at cameras.
Kim has captivated media attention and fascinated the public since her arrival on Friday.
The personal invitation from Kim was delivered by his younger sister, Kim Yo Jong, during talks and a lunch Moon hosted at the presidential Blue House in Seoul. South Korea's presidential Blue House also had no immediate comment.
Joseph DeTrani, former US special envoy for nuclear talks with North Korea, said Moon should make it clear to Kim that he wants to discuss the nuclear and missile issues at the summit. It was built in the 1960s under the government of late anti-communist dictator Park Chung-hee as a luxury facility for USA troops stationed in South Korea.
"I am very confident, as President Trump is, that President Moon will continue to stand strongly with us in our extreme-pressure campaign", Pence told NBC in an interview on Friday, maintaining all options were open to deal with the crisis. The two did not interact - although Pence, who arrived late, greeted the other dignitaries around him - prompting criticism of the American vice president.
In previous years, North and South Korea have held reunions to bring together family members who have been separated by the war. But rather than presenting herself as a stiff party operative, she has looked engaged and interested during multiple outings in Seoul, Pyeongchang and Gangneung.
The invitation had sparked concern that Kim had succeeded in driving a wedge between South Korea and the USA, which have differed on the best way to rid North Korea of nuclear weapons. Before now, she had been seen mainly in photos, but often in the background, as her brother took center stage.
She verbally conveyed Kim's invitation to Moon "to visit the North at his most convenient time", he added.
The most important part of the visit, however, came during one of the quieter moments.
A visit by Moon to the North would be only the third inter-Korean summit to take place.
This photo, taken on February 10, 2018, shows President Moon Jae-in (R) receiving North Korean leader Kim Jong-un's letter from Kim Yo-jong, the younger sister of the North's ruler, at Cheong Wa Dae.
This story has been corrected to show that the North Korean delegation stayed at the Walkerhill, not Wakerhill, hotel.
The Moon government has been engaging in a delicate balancing act between Pyongyang and its longtime ally Washington after Kim Jong Un offered to send a delegation to the Olympics in the South. Moon has accommodated the North's demands on Olympics participation in hopes of persuading Pyongyang to return to the negotiating table to discuss denuclearization, while trying to allay concern in Washington that the North was using a "charm offensive" to simply ease sanctions and earn time to complete its nuclear weapons program.
The prospect of talks comes after months of tension between Pyongyang, Seoul and Washington over North Korea's pursuit of nuclear weapons, with US President Donald Trump and North Korean leader Kim Jong Un trading insults and threats amid tightening sanctions from the United Nations.