Surely sex is not a sin by default, right?
Young, single people, healthy and horny, end up having lots of sex. What's wrong with that?
And some of the good looking ones realize they can make (good) money out of it. If they're not in a committed relationship, then again, what's wrong with that?
This is compounded by the fact that job opportunities are limited for women in Japan. They're expected to marry and become housewives! So because of that, companies don't invest in women in the workforce because they expected them to marry and quit.
Anyways, that's probably for another discussion. I have a lot of thoughts on that topic
But to go back to the original question:
I do know of a former escort who got married to a guy few years ago (and he does know of her past). I don't know them directly, so I don't know for sure how well things are going, but they're still married, so there's that.