Sunny debuted in 2007 as a member of Girls' Generation under SM Entertainment.
Sunny and SM Entertainment announced on Aug. 08, 2023, that she will leave the agency upon contract expiration. Sunny stayed with the agency for 16 years.
"With courage, I plan on looking at myself in a different environment, with a different perspective," she wrote on her Instagram on Aug. 08. 2023.
"I would like to thank SM Entertainment, who helped me immensely so the 19-year-old Lee Soon-kyu could debut as Sunny in the group Girls' Generation," she wrote, thanking her fans, agency and the staff she worked with over the past 16 years.