Hayoung (BADKIZ)

On June 21, 2018, Hayoung made her solo debut with the release of the digital single "Secret". On September 16, 2018, she performed with the girl group BADKIZ for the first time. She was officially introduced as a new member of the group four days later on September 20, 2018, with a handwritten letter.

However, in February 2019, she was assumed to have left the group after her contents were removed from the group's SNS accounts. She was the only former member at the time who never participated in any music release.