Four women accompanied Mr. Kim Jong-un at the conference in Hanoi.

North Korean leader Kim Jong-un arrived in Vietnam by train yesterday after traveling from Pyongyang via China. He was accompanied by his sister Kim Yo-jong and leader of the Moranbong band Hyon Song-wol.

After arriving at a hotel in Hanoi, Chairman Kim Jong-un met with aides, including two women: head of the tactical office of the Korean United Front Department Kim Song-hye and Vice Foreign Minister Choe Son-hui.

Kim Yo-jong, sister of North Korean President Kim Jong-un, steps down from the Dong Dang train station in Lang Son province on the morning of February 26. Photo:Huu Khoa

Kim Yo-jong, born in 1988, studied abroad with him in Switzerland when he was young. She has served as Deputy Director of the Propaganda and Agitation Department of the Workers' Party of Korea since 2014, tasked with strengthening and building her brother's image. In October 2017, at a meeting of the Central Committee of the Workers' Party of Korea, Kim Yo-jong was appointed as an alternate member of the Politburo.

Kim Yo-jong is tasked with handling propaganda, from government statements to press releases and films. But North Korea expert Michael Madden says her actual role goes beyond her official duties. He describes Kim Yo-jong as a White House chief of staff, involved in everything from the basics to the big decisions: nuclear missile testing, intelligence, foreign policy, schedules, logistics and security for Kim Jong-un.

Ms. Kim has accompanied her brother to many summits with international leaders, including with South Korean President Moon Jae-in, Chinese President Xi Jinping and the first summit with US President Trump last June. She showed meticulous attention to details, such as giving Mr. Kim a pen to sign documents in Singapore instead of letting him use the pen prepared by the US delegation.

When the armored train carrying Mr. Kim Jong-un stopped at Dong Dang station in Lang Son province yesterday, Ms. Kim got off the train first to observe the surrounding situation. When Chairman Kim Jong-un got off the train to talk with Vietnamese officials, she quickly went to the black limousine in front of the station to wait for her brother.

Hyon Song-wol (center) in Korea in early 2018. Photo:AP.

Hyon Song-wol, born in 1977, was the lead vocalist of the famous pop group Pochonbo Electronic Ensemble in the early 2000s. South Korean media said Ms. Hyon had known Mr. Kim Jong-un since his childhood, when he returned to North Korea after studying abroad in Switzerland.

She married a North Korean officer in 2006 and has a child. Hyon is not only a pop icon in North Korea but also involved in politics. In 2017, she was elected to the Central Committee of the Workers' Party of Korea.

Ms. Hyon is the leader of the Moranbong band, formed in 2012, consisting of 10 beautiful members with a modern fashion style rarely seen in North Korea. The group plays pop, rock or a combination of many genres and is often compared to the Spice Girls of North Korea. The members of the group are said to have been personally selected by Mr. Kim Jong-un, according toStraits Times.

In early 2018, Hyon Song-wol led a large art troupe to South Korea to perform for the Pyeongchang Olympics and made a strong impression on the South Korean public. Many compared her style of dress to that of US First Lady Melania Trump.

"Ms. Hyon is a lively person and very loyal to Mr. Kim," a South Korean intelligence official said, according toChosun Ilbo.

Kim Song-hye (left) and South Korean officials during a meeting at Panmunjom in 2013. Photo:Ministry of Unification of Korea.

Kim Song-hye, born in 1965, participated in many negotiations between South Korea and North Korea such as the inter-Korean summits in 2000 and 2007. She was also in charge of welcoming South Korean officials visiting Pyongyang such as Congresswoman Park Geun-hye (who later served as South Korean president from 2013 to 2017) in 2002 and former South Korean first lady Lee Hui-ho in 2011.

It is rare for a North Korean woman to work in the field of inter-Korean relations, so Ms. Kim Song-hye has been nicknamed "the hard-working female official for Korean affairs." In February 2018, she accompanied Ms. Kim Yo-jong in the North Korean delegation to the Winter Olympics in South Korea.

North Korean Vice Foreign Minister Cho Son-hui at the Ritz-Carlton hotel on June 11. Photo:AFP.

Choe Son-hui, born in 1964, is the highest-ranking female diplomat in North Korea. Vice Foreign Minister Choe is the daughter of former North Korean Prime Minister Choe Yong-rim, who held the position from 2010 to 2013, so she has close ties to the ruling Kim family.

She studied in North Korea, China, Austria, and Malta, and has extensive experience negotiating with the United States and discussing the nuclear program. Choe Son-hui served as an English interpreter for the North Korean delegation to the six-party talks on nuclear disarmament in the 2000s, but those efforts failed.

In preparation for the first Trump-Kim summit in Singapore last year, Choe led the North Korean delegation in negotiations with US officials. In May 2018, she called US Vice President Mike Pence an “idiot,” prompting Trump to cancel the summit, but he quickly reversed his decision. Some observers at the time believed that Kim Jong-un would fire Choe, but she would remain in office.

Ms. Choe is "very smart and well-connected," said Ralph Cossa, president of the Pacific Forum Center for Strategic and International Studies.

All four women accompanied Mr. Kim to his first summit with Mr. Trump in Singapore. Some experts believe the presence of the four women may be part of North Korea's strategy to impress world leaders and change how they view North Korea.

“Gender balance in politics is an increasingly important issue in many countries, and North Korea wants to be seen as keeping up with the times,” said Sarah Son, research director at the Transitional Justice Working Group, a South Korean NGO.