Whomever said prostitution was underground in tokyo lied

While walking around the city last night I was approached not once, not twice, but SEVEN times by women asking me if I wanted a "special massage" for prices ranging from 5000-10000 yen (50-100US roughly). I could understand if I was in the Red Light district, but I am in central downtown tokyo! I have heard Roppongi is famous for this, but I'm nowhere near it!