Seung-hee would work twelve hours per day at a gimbap store to support the family and pay for Lee's skating.

[7][6] In 2016, Lee's mother tore her rotator cuff ligament from rolling gimbap too hard, making her unable to work.

Eventually, The Green Umbrella Children's Foundation learned of Lee's situation and agreed to pay for his training fees.

[10] Lee began figure skating at the age of ten after being inspired by Yuna Kim's victories at the 2009 World Championships and 2010 Vancouver Olympics.

Making his senior international debut, Lee also competed at the 2016 CS Ondrej Nepela Memorial, where he placed eleventh.

[11][12] Although assigned to compete at 2018 Junior Grand Prix Canada and 2018 Asian Open Trophy, Lee withdrew from both events.

Cha Jun-hwan's tenth-place finish at the 2021 World Championships earned two spots for men's singles at the 2022 World Championships and provided the opportunity for Korean men's singles skaters to earn a second berth for the 2022 Beijing Olympics at the Nebelhorn Trophy, the final Olympic figure skating qualifying event.

After winning the silver medal at the 2022 Korean Championships, Lee was named to the Four Continents, Olympic, and World team for South Korea.

"[17] At the 2022 World Championships, Lee scored a personal best in the short program, finishing thirteenth in that segment of the competition but dropped to eighteenth overall following an error-ridden free skate.

During those championships, Lee expressed his support for Ukraine following Russia's invasion by having a Ukrainian flag patch pinned to his jacket.

[18][16] Lee began the 2022–23 figure skating season with a silver medal win at the 2022 CS Nebelhorn Trophy, where he scored a new personal best in the short program.

[24] At the national Ranking Competition, Lee came in ninth-place and ultimately wasn't selected to compete at the 2024 Four Continents Championships as a result.

[25][26] He followed this up by winning his fourth national silver medal at the 2024 South Korean Championships and was named to the 2024 World team.

[29][30] In late November, Lee would compete at the annual South Korean Ranking Competition, where he won the bronze medal.

[31] One month later, he won the bronze medal at the 2025 South Korean Championships, earning a spot on the 2025 World team.