Although it’s illegal, there is little stigma attached in South Korea to males that frequent prostitutes (the inverse doesn’t hold).

It’s not unusual for university-aged men to have nights out with friends at brothels. Ergo, there’s a strong chance that the police trained for this at the academy. ():

Setting guidelines for cracking down on prostitution last March, the Supreme Prosecutors Office instructed its agents raiding businesses of ill repute to pretend to be customers and have sex with the working girls in order to secure evidence. Actually, one group would go in pretending to be customers, while the other would come in slightly later to bust the pimps after the other group had secured the evidence, so to speak. Agents were further encouraged to pay pre-arranged service fees on their credit cards for further evidence.