As Japanese birth rates plummet amid a generational fertility crisis, experts have fingered an explosion in sex dolls as an emerging threat to the country's already-dire population problem - with some even saying they will lead to the "extinction" of the Japanese race.

According to the RT documentary "Substitutes," industry insiders say that around 2,000 life-like sex dolls - with adjustable fingers, removable head and customizable genitals are sold annually in Japan. Assuming costs come down and the Japanese workforce continues to put in 14-hour days, there could be tens of thousands of sex dolls floating around the island nation within a decade. Maybe don't look in random closets when visiting friends in Japan.

For sex doll salesman Noburu Tanaka, the advantage of owning one of the ¥420,000 ($3,750) synthetic dolls is its lack of expectation. “It’s an amazing feeling. It looks like a doll, but you feel as though it’s really alive,” he told RT. “When you make love to your wife, there can be some problems. With a doll, none of that matters.” For Kanako Amano, a demography expert at the NLI Research Institute in Tokyo, the dolls pose an existential threat to the future of a country where the population is estimated to decline by a third in the next 30 years. -RT

"The biggest problem in Japan is the decline in birthrate and population. It’s being called a national disaster,” said Amano. “The Japanese are at a crossroads, facing the threat of extinction. We’re an endangered species."

In the early 1950s, fertility rates hovered at a healthy 2.75 children per woman, UN data shows. By 1960, as businesses asked more and more of their employees, the fertility rate had fallen to 2.08. Japan had sunk to a critical threshold known as "replacement fertility," the bare minimum to avoid losing population. "In those days, women's university enrollment rate exceeded 40%," Tokyo University economist Hiroshi Yoshida tells Business Insider. But as more women entered the workforce, fertility began to plummet. Today, more than 50 years later, Japan's fertility rate sits at 1.41, the population is falling, and brutally long work hours remain the norm. -Business Insider

That said, "loneliness among older people" appears to be one of the main drivers of the rise in sex dolls in Japan. Sell doll owner Moru, for example, purchased his polymer companion after the death of his wife.

There was a void in my heart,” he told the documentary team, as he pointed at the row of dolls arranged in a sitting position on his couch. “When I met them, my life became inextricably bound to them. Since these girls appeared in my home, and thanks to them, I haven’t felt that lonely anymore…” -RT

Moru and his friend Keroro - who owns up to 20 dolls - take drives or trips together to parks, where they pose the dolls on benches and other locations to take photographs.

Rise of the love machines? People will soon be losing their virginity to robots - academic https://t.co/z8u3Y3HNTl pic.twitter.com/CuHvlMZ8eB — RT (@RT_com) June 11, 2016

And its not just men!

Female model Hitsuji who is very popular with Japan's youth says she adores her doll Masiro - and says she has no desire to live with man. “Masiro is not a friend, a family member or a loved one. She’s a creature who accepts my love,” she said. “I have never consorted with men like that.”

China and Hong Kong, meanwhile, has been suffering from similar low fertility rates amid an epidemic of "grass-eating men" - lame, feminized Chinese man-children who refuse to step up their game and get laid.

Indeed, Hong Kong is suffering from an army of loners - estimated at 20,000 to 40,000 strong - usually in their 20's and 30's, who are choosing video games, anime and internet porn over wives, sex and the inevitable children that follow.

We can blame the prevalence of smartphones, laptops, computers, tablets and other electronic devices. We can even blame it on e-sports, a new pseudo sport that is sweeping the city with government backing. It can also be interpreted as another excuse for people to submerge themselves in the digital world rather than experience the real word. -SCMP

These sexless men are known as "otaku," - a Japanese term for socially awkward gents who have isolated themselves from their families and romantic prospects alike. "[T]hese “geeks” tend to be diehard anime and manga fans who have little interest in dating," writes Luisa Tam in the South China Morning Post.

Taking it one step further are the "soshoku danshi," which translates to "grass-eating men" or "herbivore men" - a term coined by Japanese columnist Maki Fukasawa who describes these particular isolationists as having a "monk-like approach to life and relationships," which of course includes no sex.

Studies in Japan estimate that this class of men, normally in their 20s and 30s, account for around 60 per cent to 70 per cent of the male population. Obviously, their reluctance to procreate is a major cause for concern. Japan has had one of lowest birth rates in the world for nearly a decade now. -SCMP

Hong Kong has seen a sharp rise in the number of "grass-eating men," according to Dr. Paul Wong Wai-ching, associate professor of the Department of Social Work and Social Administration at hte University of Hong Kong.

And while some experts have argued that slower population growth could mitigate pressure on China to create new jobs as technology increases productivity, others think China is in deep trouble...

“They should have lifted all birth restrictions before 2010,” says Baochang. “Whatever steps they take now, China’s low-fertility trend is no longer reversible.” In three decades, 1/3 of China's population is predicted to be over the age of 60.

Meanwhile, China's one-child policy, and now two-child policy, has conditioned the population to shun large families.

In a generation that grew up without siblings, a one-child mind-set is deeply entrenched. Maternity-leave policies have been expanded but some women say taking leave twice is a career impediment. An All-China Women’s Federation survey found 53% of respondents with one child didn’t want a second. Even without birth limits, China’s economic development would have reduced fertility rates, says Martin Whyte, a Harvard University Chinese-studies expert. That has been the pattern elsewhere in the world: When incomes rise, the sizes of families tend to go down. -WSJ

If the nation drops birth policies now, says Whyte, “China will learn what many other countries have learned—that it is much more difficult to get people to have more babies” than to force them to stop having them.