Japanese women, for their part, often avoid romantic relationships because Japanese laws and social norms can make it extremely difficult for women to have both a family and a career. Japan is extremely unusual in that it is highly educated and wealthy but still has some of the worst systemic gender inequality in the world; it has a European-style economy but South Asian social family mores. Professional women are stuck in the middle of that contradiction. It's not just that day-care programs are scarce: Women who become pregnant or even just marry are so expected to quit work that they can come under enormous social pressure to do so and often find that career advancement becomes impossible. There's a word for married working women: oniyome, or "devil wives."

Because they're forced to choose, inevitably lots of women who might otherwise have a family and a job are only seeking the latter. That sense of pessimism about marriage appears to be partially driving the lack of interest in romantic relationships, and thus in sex. This chart shows common reasons expressed for staying single, by Japanese men and women ages 25 to 34. The shaded bars represent the subsequent national surveys, from 1987 through 2011:

It appears so, for the most part.