South Korea's Lee wins gold at Four Continents
The teenager, who came sixth in the short programme, scored 141.71 points in the women's free skate event to take her total to 210.84.
Fellow South Korean Kim Ye-lim, who finished first in the short programme, won the silver, and another teen, Japan's Chiba Mone, came from seventh to win the bronze.
"I always try to do my best, but this time I tried not to think about my results and focus on my training process," said Lee, who claimed silver at the event last year.
"I think I did well, so I'm happy right now."
Earlier, reigning world silver medallists Riku Miura and Ryuichi Kihara of Japan took the lead in the pairs short programme, scoring 71.19, less than two months after travel delays forced them to miss Japan's national championships.
The pair, who performed to "You'll Never Walk Alone", completed a triple twist, throw triple Lutz and level-four lift, spin, footwork and death spiral.
Miura fell on their side-by-side triple toe-loops, but they managed to edge out Canadians Deanna Stellato-Duek and Maxime Deschamps, who sit second with 68.39 points.
"I was nervous and therefore I made the mistake. I will try to switch my mindset for tomorrow," Miura said.
"Although I made a mistake, we were able to score higher than 70 points. That shows what we've been accumulating in the past and I think it's a proof of how we grew."
In rhythm dance, local hopes Madison Chock and Evan Bates held off Laurence Fournier-Beaudry and Nikolaj Sorensen of Canada for a narrow lead.
Americans Chock and Bates, aiming for their third win at Four Continents after 2019 and 2020, posted a season's best of 87.67 points, while Fournier Beaudry and Sorensen came second with 86.28. Marjorie Lajoie and Zachary Lagha, also from Canada, sit third.
Four Continents, which features the top international skaters from outside of Europe, marks the final major event ahead of next month's World Championships, set to be held in Saitama, Japan.