Sung-bin won the men's skeleton, giving South Korea its second gold of these Games and its first Winter Olympics medal ever in a non-skating event.
Nikita Tregubov, who competed as an Olympic Athlete from Russian Federation, was 1.63 seconds off gold, while England's Dom Parsons took bronze.
The semi-finals are set for February 19 followed by the bronze medal game on February 21.
Roared on by the home crowd on the start of a lunar new year observed in Korea, the 23-year-old stormed to his country's second gold medal of the Games - with plenty to spare.
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Yun built a lead of more than one second after three runs, ensuring that only a major error - which he averted - in the final heat could rob him of a highly-anticipated gold medal in front of a home crowd that has closely followed the popular athlete's Olympic journey.
"It is not my effort alone that got me this medal". In an event that until now had been dominated by Western athletes, he became the first Asian to win gold in skeleton at the Winter Olympics. Norway claimed the champion in a time of 51:24.3.
Yun finished 16th in his Olympic debut at the 2014 Sochi Games, just two years after he took up the sport.
The United States has five golds, one silver and two bronze medals so far in Pyeongchang. She repeated as the gold medal victor after also taking first place in Sochi.
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The Indian shot middle rounds of 69-67 at Riviera to lie just outside the top 10 with a round to play before settling for T26. It's like a first date kind of thing. "It's tiring", McIlroy said after Friday's second round with Woods and Justin Thomas .
"I didn't show 100 percent, so I will show 100 percent (Friday)", Yun said. "In the past year I have been going there in front by myself but I had to try and push hard all the way and I knew I could do it if I had a good day", said Bjoergen, who started her final leg in third place.
"It feels unbelievable to win Olympic gold", said Yun.
Head coach Lee Yong said Yun knew the curves and turns of the Olympic Sliding Centre better than anyone.
He was the most consistent performer throughout the competition as he headed into his fourth and final run with an incredible lead of more than a second.
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