Aged 12, Lee caught the attention of FC Barcelona after he finished as the top scorer in the 2010 Danone Nations Cup, one of the most prestigious youth football tournaments.

[5] He was also named the best player in four youth tournaments: Torneo Canillas,[6] Memorial Gaetano Scirea,[7] Trofeo San Bonifacio,[8] and Gabala Cup.

[11] On 31 August 2017, Lee joined Serie A club Hellas Verona on a four-year deal, for a fee of €1.5 million.

[15] He was excluded from the list of the squad for twelve consecutive matches, and this situation caused much controversy in South Korea.

[22] On 1 February 2021, Lee joined Primeira Liga side Portimonense on a six-month loan deal with an option to buy.

[24] Lee still showed weak physical strength, pace and defensive skills, which had been followed by his failure in Italy and Belgium,[25] but his accurate shots and momentary movements stood out in South Korea.

[27] In his second season, Lee struggled somewhat due to his weaknesses grasped by opponents,[25] but helped Suwon avoid relegation by scoring the most goals among team members.

[28] He received an offer from Seire A club Frosinone in the middle of the season,[29] but was more cautious about his challenge in Europe after the hardship at Sint-Truiden.

[32] Lee made his international debut as a part of the South Korea under-16 team in the 2014 AFC U-16 Championship qualification.

Lee played for South Korea in the 2015 FIFA U-17 World Cup, but he missed a crucial penalty against Belgium.

In a friendly against Honduras just before the 2018 FIFA World Cup, Lee made his senior international debut and showed impressive performance including an assist.