After class, the women ordered tea and sandwiches at a restaurant a few floors down. Ms. Shirota pulled out her phone to show pictures of her summer trip to Ireland. One classmate, a married mother of three teenagers, reminisced about a family trip there years earlier, lamenting how she had not returned because of the prohibitive cost of airline tickets for a family of five.

Some men are reacting to Japan’s economic realities by shying away from marriage as well. Ever since Japan’s speculative stock and property bubble burst in the early 1990s, wages have flatlined. The long-held social compact between employers and workers — in which few people were ever laid off and employees were guaranteed lifelong employment — has diminished. About one-fifth of men are now consigned to irregular contract jobs that offer little stability or potential for advancement.

With the social expectation that men should be the primary breadwinners, many men worry they will struggle to support a household financially. Just over a third of men ages 35 to 39 have never been married, up from less than a quarter 20 years ago.

“Nowadays, men’s wages are not growing, so they don’t make enough to support their own families,” said Kazuhisa Arakawa, a senior director at a marketing firm who wrote “Super-Solo Society” and “The Rise of the Solo Economy.”

Mr. Arakawa, who came of age in the late-bubble years and is single himself, says that many of his male peers view marriage as an encumbrance.

Of course, matters of the heart do not strictly conform to economic conditions. Remaining single is often less of a deliberate stance than a reflection that the urgency to get married has diminished in today’s society, experts say.

“The data suggests very few women look at the lay of the land and say ‘I’m not going to marry,’” said James Raymo, a professor of sociology at the University of Wisconsin-Madison who has written extensively about marriage in Japan. Rather, he said, they “postpone and postpone and wait for the right circumstances, and then those circumstances never quite align and they drift into lifelong singlehood.”