Singer and actor Park Yoo-chun on Monday filed a counterclaim against the first woman who had filed a sexual assault complaint against him.
She withdrew the complaint a few days after filing it, reports The Korea Herald.
Park's complaint against the woman involves claims of a false statement and blackmail.
Park's legal representative from the law firm Shin & Kim filed the complaint at Gangnam Police Station on Monday afternoon.
Park is reportedly considering whether to file similar complaints against the second, third and fourth women who filed sexual assault claims against him.
The police investigation team in charge of Park's case, which previously had six members, has now been boosted to 12, police said.
Police plan to summon Park for questioning once they have questioned the first alleged victim, others who were present at the scene and the owner of the bar where the alleged sexual assault took place.
On June 10, a woman in her 20s filed a sexual assault complaint against Park, 30, who is a member of K-pop group JYJ.
She then withdrew the complaint on June 15, saying there had been "no coercion during sexual intercourse with Park."
A second woman filed a sexual assault complaint against Park on June 16 and two more women came forward with sexual assault complaints against Park the following day.
The first woman, before withdrawing her complaint, had claimed that she was sexually assaulted by Park on June 4 this year inside the bathroom of a bar where she was working.
Police are reportedly considering widening the investigation to look into potential charges of illegal confinement and prostitution.
Park's agency C-Jes Entertainment released a statement Sunday saying they have "evidence to prove Park's innocence" and will "comply with police investigations."