Before becoming a trainee, Sung Hoon was a professional figure skater who competed in various competitions. He won silver at the Asian Figure Skating Trophy twice, during different years, and participated in the Korea Figure Skating Championship in 2018
On June 1, 2020, Sung Hoon was introduced as a contestant in the CJ ENM, and Big Hit Entertainment’s reality survival show I-LAND. On September 18, 2020, he ranked 6th place by global votes and became a member of the boy group ENHYPEN.