"He was very natural when he talked about various topics from music, culture to sports," South Korean Culture Minister Do Jong-hwan told CNN.
Do sat near the North Korean leader and his wife, Ri Sol Ju, as they waved at the crowd and applauded the first performance of South Korean stars in Pyongyang in more than 10 years.
The concert, featuring K-Pop music which in the past has been banned in North Korea, was one of the clearest signs of thawing relations ahead of a planned summit this month between Kim and South Korean President Moon Jae-In.
Do told CNN he was optimistic about the summit, saying Kim seemed "sincere and genuine" about wanting to improve relations with Seoul.
He added that after the performance -- titled "Spring is coming" -- Kim noted the symbolism of the name and hoped for a similar cultural exchange in Autumn, after the summit with Moon and a planned meeting with US President Donald Trump, which is still be to scheduled.
"For him to propose a performance in Seoul in the Autumn after having two successful summits shows that his willingness to participate in the two summits," Do said.
Pyongyang outreach
Since then, a North Korean delegation traveled to South Korea to participate in the Winter Olympics, officials met several times at the demilitarized zone between the two countries, and Kim himself traveled to Beijing for a meeting with Chinese President Xi Jinping, his first with any foreign leader since taking power.
That Kim agreed to travel to Beijing suggests that China is determined to have a say in the talks, while not being at the table during both the Moon and Trump summits.
This week, Kim presented an "in depth analysis about the improvement of the inter-Korea relations and the talks between North Korea and the US" to a meeting of the North Korean Worker's Party politburo, according to the state-run Korean Central News Agency (KCNA).
This was the first time Kim had mentioned the talks with Washington, and a sign, according to Anwita Basu, an analyst at the Economist Intelligence Unit, that he is committed to pursuing a "significant thawing in North Korea's relationship with the international community."
"It is apparent that his focus, at least in the short term, is on reviving the economy. Tighter sanctions have started to impact livelihood and arguably government revenue," she said in a statement.
While North Korean and US officials are discussing the agenda for the meeting, Basu predicted Pyongyang will not bend much on denuclearization, a key demand of the Trump administration.
"A lot of the diplomacy will be a means for them to push back tighter sanctions in exchange for a freezing (in the short term) of the nuclear program," she said.
Do, the South Korean official, was optimistic about the talks, pointing to a consensus among major powers that the situation on the Peninsula had been deteriorating dangerously.
"If it doesn't work out, it's bad for everyone, to South Korea, China, North Korea and the US," he said. "If it does work out, meaning both the inter-Korean and nuclear issues get resolved, it's good for everyone."
Paula Hancocks reported from Seoul, South Korea. James Griffiths reported from Hong Kong. CNN's Yoonjung Seo contributed reporting.