Yong Jun-hyung, 29, who is a member of boy band Highlight -- formerly known as Beast -- said he watched a video of singer Jung Joon-young having sex with women taken without their consent.
Jung, 30, was questioned by police on Thursday after admitting he shared the footage with other men, including mega K-pop star Seungri, who is also embroiled in a sex-for-investment criminal investigation.
Both Seungri -- a member of boy band BIGBANG -- and Jung, announced their retirement from show business earlier this week.
Yong "has watched the footage... and had an inappropriate conversation with (Jung)," the singer's agency Around Us Entertainment said in a statement, adding Yong will leave the band Highlight on Thursday.
South Korea has been battling a growing epidemic of so-called "molka", or spycam videos -- mostly of women, secretly filmed by men.
As well as secretly filming women in schools, toilets and offices, "revenge porn" -- videos men take of themselves having sex with their exes or partners filmed without the women's consent -- is believed to be equally widespread.
According to Han Sol, an activist at Flaming Feminist Action, such videos have long been watched and shared by South Korean men as a form of entertainment and a way to strengthen their "brotherly ties".
Yong, who has also worked as a record producer and actor, previously denied allegations that he had been involved in the ongoing K-pop sex scandal.
For South Korean women's activists, the scandal, including the latest revelation, is unsurprising.
Thousands of women protested in Seoul last year on several occasions against spycam and revenge porn videos, as part of the country's ongoing #MeToo movement.
"This case just shows that male K-pop stars are no exception when it comes to being part of this very disturbing reality that exploits women," women's rights activist Bae Bok-ju told AFP.