Former comfort women did not publicly state that they had been abducted until after Yoshida falsely claimed that he forcibly rounded up Korean women in his 1983 book. The subsequent media coverage (especially by Asahi Shimbun) created a torrent of anger, whereby later investigations disproving Yoshida’s account were largely ignored. Before the comfort women issue became worldwide news, most Korean comfort women survivors stated that they had been “sold” by their parents or became comfort women of their own accord, albeit possibly deceived by recruiters about the nature of work. (Ref. 2) There were clear exceptions, such as in Indonesia (mentioned above) and the Philippines, and there were instances of women being taken away by civilian agents and recruiters, not by the Japanese military in an official, institutionalized capacity.
Abduction of women for sexual exploitation was a crime that Japanese police took seriously and addressed when discovered, arresting the traffickers and rescuing the victims: http://scholarsinenglish.blogspot.com/2014/10/korean-newspaper-articles-from-1930s.html
As such, for women on the Korean peninsula who were indeed abducted and taken to brothels, most are almost certainly attributable to unlawful civilians whose criminal activities evaded Japanese police. Additional information on abduction of women for sexual exploitation by civilian criminals is available (e.g., “Comfort Women and Sexuality on the Battlefield,” by Ikuhiko Hata, Shincho Sensho, Tokyo, 1999, pp. 53-54).