"Japanese women tend to seek men with stable employment and education levels" higher than them, he explained.
Anecdotal evidence from the match-making party seemed to bear this out, a small queue of women forming to exchange contact details with one of the men who, it emerged, had the highest income of the group.
"The high ratio of unmarried men and women won't change unless more women accept the idea of marrying a man with an income lower than herself," said Yamada.
In addition, many people meet future spouses in the office in workaholic Japan, and there are fewer opportunities as jobs become more precarious.
In the decades after World War II, Japan rebuilt its economy largely via huge corporations offering ultra-dedicated workers a job for life -- but that pattern is changing rapidly and job security is declining.
Since the early 1990s, the ratio of non-permanent and contract employees has risen from around 15 percent to just below 40 percent, according to labour ministry statistics.
Focus on love
"Lower levels of income and an increase in the number of extremely unstable jobs -- with the fear of getting sacked at any time -- are not helping people to think about getting married and having a family," said Shuchiro Sekine, head of a trade union representing contract workers.
Even if these workers hope to find a partner, with less job security and lower income comes less chance of finding a spouse.
Six out of 10 men aged between 30-34 with a classic "salaryman" job were married as of 2017, according to a government study issued this year, whereas only 22 percent of male contract workers the same age had a wife.
Those at the Tokyo match-making party are the lucky ones, Sekine told AFP. "Those on lower incomes wouldn't even think about attending."
Despite these barriers, do such events help? Shoji Wakisaka, head of the association hosting the party, said there was no firm data but there had been some successes -- if limited.
"About two percent of participants on average find a spouse."
One single woman at the party said it was an "efficient" place to meet others who want to get married.
"You can't exactly ask passers-by if they are married," her mother added.
A marriage counsellor at the party, Noriko Miyagoshi, implored would-be lovebirds to forget the finances and focus on Cupid's arrow.
"You shouldn't be making a lot of conditions," she told participants. "I hope you choose the one you genuinely feel you'll be able to get along with.