[4][5] On October 1, 2015, Starhaus Entertainment launched the project group One O One, releasing their debut single "Love You".

The group consists of Kwak along with fellow Starhaus actors Ahn Hyo-seop, Song Won-seok and Kwon Do-kyun.

[6] Kwak gained popularity after starring in the hit romantic comedy drama Oh My Ghost, portraying a chef who appears stand-offish but is kind and sweet.

[7][8] He then starred in daily drama All is Well [ko],[9] and joined the reality show We Got Married where he was paired with actress Kim So-yeon.

[26] In 2020, he joined the SBS sci-fi drama Alice as time traveler Yu Min-hyuk.