In 2016, Sei became a contestant on Mnet's new survival show Produce 101, representing her company LOUDers Entertainment. She was eliminated in the episode 5 after achieving 85th place. After the show, she left her company and signed with Fantagio Music.
2017: Debut with Weki Meki
In August, 2017, she debuted as a member of the girl group Weki Meki, with former Produce 101 contestants Yoojung, Doyeon and Elly.