Had one crazy experience a few years ago. Was in a karaoke bar in a hotel (not a room ktv, but a stage). Ended up being approached by another foreigner with the mamasan together. The mamasan was too shy
because of her lack of English to approach me. The other foreigner could speak Canto...
My experience is that most hotels have some sort of accomodation, being it the beauty/hair salon, the massage/sauna or the ktv/nightclub.
Outside of hotels I have not much experience. One time a local massage parlor where they were asking if I wanted massage witha big wink and some streetwalkers asking if I wanted massage.