“The past century is a history of sexual distortion,” social psychologist Hiroyoshi Ishikawa told Time Magazine in 1983.

“A small portion of young people in Japan are sexually very, very active,” he added, “while the vast majority are sexually repressed.”

What would he say if he surveyed the scene today? Probably that not much has changed in 30 years — except that the “small portion” grows steadily smaller.

Japan is a lonely, lonely country, if two reports, one in Spa magazine and the other in the weekly Aera, reflect the true state of things. The former focuses on single life, the latter on marriage. Both come across as sad, abject, mournful failures. You wouldn’t choose either, if you had a choice — and what else is there?

Spa polls 600 single men aged 35-45. They are some of the freest people on Earth — accountable to no one, responsible for no one, well enough off financially. They can do whatever they want, whenever they want. Why are they miserable?

“I was sick, I had a noro virus,” recalls a 41-year-old executive — “and there was nobody around to even bring me a glass of water.”

“Who can I go traveling with?” sighs a 38-year-old civil servant. “All my friends are married and have kids — they can’t come with me.”

“With someone you love, even McDonald’s would be delicious. With my parents, the best-cooked meal is just a chore to slog through,” complains a 39-year-old banker.

“Everyone at work is forever going on about child-care issues — ‘day-care centers in my neighborhood give you such a warm welcome; medical treatment for kids is free,’ and so on and so on. What am I supposed to contribute to this?” grumbles a 38-year-old office worker.

“I see all those happy families,” confides a 45-year-old businessman, “and think to myself, ‘Even if I get married tomorrow’ — which isn’t going to happen — ‘I’ll be 57 when my kids are that age.’ “

Other questions aside, are “all those happy families” really so happy? Not if we believe Aera, whose subject — not the anomaly it sounds — is sexless marriage. Between 40 percent and 50 percent of all marriages in Japan are said to be sexless.

In old Japan, marriage was essentially a device to produce family heirs. That done, husbands typically pursued love, eros and romance in the licensed pleasure quarters while wives seethed at home in silent frustration. The sexless marriage of today is different. Aera cites research by gynecologist Kunio Kitamura showing its leading causes: for men, fatigue from work; for women, a weary feeling that “sex is more trouble than it’s worth.”

Psychiatrist Teruo Abe tells Aera of a new, or newly identified, syndrome among married couples: “sex disgust syndrome.” It seems a predominantly male affliction. It is not impotence; merely a sexual aversion for one’s wife — rooted, according to Abe, in a tendency for the marital relationship to evolve over the years into a quite different relationship: mother-son, for example, or sister-brother, or friend-friend (never father-daughter, it seems). In some cases one spouse becomes the other’s “mascot.” And sometimes, of course, there arises outright mutual hostility, not to say hatred.

Mother-son is most common, says Abe — which explains the “disgust” characteristic of the syndrome. It is, he adds, very difficult to cure.

Shouldn’t singles, instead of brooding over their loneliness, count their blessings? Why should a man get married, after all? Why should he saddle himself with family cares, family expenses, a family’s claim on his time, only to end up sexless? What’s in it for him? At least a bachelor can enjoy a syndrome-free sex life — can’t he?

Theoretically, yes; in real life, apparently not. Spa’s survey of 600 finds 72.3 percent have no girlfriend; 36.7 percent have been sexless for more than three years.

This is more than sad — it’s dangerous, warns psychiatrist Takehiko Kasuga. “It is becoming increasingly clear,” he tells the magazine, “that isolation is a factor in dementia. If you habitually spend your days off without anyone to talk to, by the time you’re into your 50s and 60s you could find yourself on the road to dementia” — or if not that, depression, to which under the best of circumstances we tend to grow more vulnerable as we age.

What has gone wrong with us? What have we done to ourselves?

Well, we work too hard; everyone knows that. It’s not entirely our fault; the economy demands it of us. Forty hours a week is considered more or less normal. Work 60 hours, and researchers consider you a candidate for karōshi (death from overwork). Gynecologist Kitamura has calculated a line beyond which we’re in danger of being too tired for sex — 49 hours.

A more subtle factor is sex education, which Japan somehow can’t seem to get right, Aera hears from Kagawa Nutrition University nutrition professor Noriko Hashimoto. She reviews Japanese sex education over the past 20 years and concludes, “No wonder we’re sexless.”

Sex education in the 1990s, Hashimoto explains, was a panicked response to the AIDS epidemic of the ’80s. Suddenly fifth-graders were handed textbooks showing mature human bodies making babies. It was too much too fast. Sex was made to look ugly, dirty, clinical. The reaction that set in seems the epitome of good intentions gone wrong. The naked human body illustrations were scrapped, and in their place — reader, you’ll never guess — copulating sea urchins.

Any questions?