The vast majority of women who end up single and childless into their forties don't do it by choice. At least not directly. They _want_ to find a partner and have children; they just didn't succeed at making the right decisions in their life to end up in that desired destination.
Arranged marriages, known as "omiai", are still a thing in Japan, especially if someone is desperate for a marriage. If a man or woman doesn't marry, that is in the vast majority of cases by choice.
