Kim's profile has been steadily rising since 2014, when she given the key regime role of deputy director of the Propaganda and Agitation Department of the Workers' Party.

Her position is such that, according to a Seoul-based think tank run by North Korean defectors, Kim Yo Jong briefly took charge of the country while her brother was reportedly ill with gout or diabetes in late 2014.

Kim Jong Un's 'gatekeeper'

But Kim's acts of public diplomacy are highly choreographed, and, like most members of the Kim clan, little is definitively known about her or her motivations, beyond her official duties.

Born in 1987, Kim studied in Switzerland like her brother, and is believed to have attended Kim Il Sung University and a European school for her higher education.

Kim was always close to her father, and after returning from Switzerland she was appointed to positions of responsibility in the government, according to Michael Madden, who runs the blog North Korea Leadership Watch.

She would act as an advance-team leader, inspecting sites before official visits and taking on administrative duties.

Under her brother's leadership, Kim has taken on more responsibility, dealing with policy, receiving intelligence briefings and acting "almost like a White House chief of staff would," said Madden.

She was promoted to the country's Politburo, the senior body of North Korea's communist party, as an alternate member last year. According to North Korea Leadership Watch, she is a close aide of her brother's "and since his accession manages his public events, itineraries and logistical needs, among other tasks."

"She's probably one of the most influential people on Kim Jong Un himself, precisely because he has very few people he can trust," said Balbina Hwang, visiting professor at Georgetown University and founder of the National Committee on North Korea.