Chowon

In 2018, she became a contestant on Mnet's reality survival show Produce 48 as a contestant representing Cube Entertainment. She was eliminated in the finale after ranking 13th place, nearly debuting with the 12-member girl group IZ*ONE. On August 21, 2019, it was announced by Cube Entertainment that Han Cho Won had officially signed an artist contract with them, but specific plans regarding her debut was yet to be decided.

On April 13, 2021, Chowon was revealed as a trainee of the pre-debut team Cube Tree, alongside Sangah and Juhyeon, through a dance practice video. On April 20, 2021, Chowon was revealed as the third member of LIGHTSUM. The group debuted on June 10 with their first single "Vanilla".