you could equally google "what percentage of Japanese are married" and see what % have married and of course consummated the marriage.

First result.

Marriage in Japan - Wikipedia

59% of the population, almost 2/3rds of the entire group surveyed are not included in that result, even if just 16% of the remaining population were having sex that would give you 75% of the actual adult population are having sex, meaning less than 1 in 4 is a sex robot banging weeb in comparison to the "almost half" which the initial click bait headline would try to push.

I wasn't going into the exact study beyond the article Final-Fan I was more interested in the sensational sex robot infested Japan filled with virgins story being incorrect and trying to make a point about how articles like this one either include or remove a group of people to fluff the numbers, in this case the obvious one I missed out on was that 59% of the population there is married and banging, of the remaining 41% of that... 42% are virgins as per the group recorded.

42% of 41% is 17.22% of the age ranges you've listed there are virgins.

Now of those 17.22% who filled out the survey and said they were virgins I'd ask you to consider taking a look at the cultural differences in Japan in some area's of dating , I found a decent read on it (fairly long) but it's interesting none the less.

https://www.japanpowered.com/japan-culture/dating-marriage-japan

But the part I was interested in is here at

"Unlike the West, Japan never associated virginity with chastity and purity. The closest idea to the Western virgin was the otome (maiden) who was thought to be lacking sexual desire in addition to experience. The Western ideas of virginity in relationship to marriage – that is,  a woman should remain virgin for her husband – didn’t appear until the 19th century (McLelland, 2010). This isn’t to say it was okay for women to have sex. During the Tokugawa Period, both men and women could be considered adulterers. Married women, unlike men, were penalized.  Women were property of husbands or fathers. Adultery was a property dispute that was left to the decision of those involved. Punishment could be everything from a fine to death"

So in recent history it has become a part of their culture that sex should be something that happens after a long relationship and often until marriage has happened, so.... while I'm not saying those 17% are all holding out for their true love, there is a chance that some % of that could be, but also a chance that a % of them answered the survey in a way which they felt their culture is more expecting them to, that is to say they're a virgin since they're unmarried since it's a loaded question with a stigma over it.

edit - Out of interest based on the final line of your post, do you not consider homosexuals to be capable of having sex? I'm not sure I understand what you were getting it?

Although, meat and dairy products tend to be bad for testosterone. Vegetarians have an average of 8% higher testosterone than those who eat meat, and vegans have 13% higher. In fact, those who are doing the all meat diet have been experiencing extremely low testosterone levels: (former) Dr. Shawn Baker, for example, a guy who obviously had high testosterone originally, got some bloodwork; not to mention it’s a source of estrogen.

I'm not a specialist on that at all. But weird, because what I found on Dr Baker website is "Numerous studies demonstrate that vegetarian, low fat or vegan diets often result in lower levels of free testosterone". In my opinion it would seem normal to need a healthy diet, so not 100% meat of course (who can be stupid enough to do something like that...).

Anyway, from what I found quickly on Google, at least Japanese middle age men have lower testosterone, and the studies mention mostly the quality of life... But it doesn't explain why part of the young men act like asexual sheeps too...

Any (credible) source for that? As a fitness enthusiast I find those claims interesting (and hard to believe).

A little more info on Shawn Baker: He's an anti-vegan and vegetables in general. While he still markets himself as a doctor, he's lost his license; and watching a few of his videos, even if it wasn't due to malpractice, it's easy to see why. When challenged to take a blood test, it showed that his testosterone levels had dropped substantially. I don't know if it is another factor, but in his recent videos Shawn Baker's voice seems to be cracking, getting a little high-pitched.

This article suggests that the reason for lower effect in testosterone in Japan is due to the environment which creates higher levels of binding agents - unfortunately, it's more of an overview and doesn't dig too deeply into details. Interestingly enough they produce 16% more testosterone than western populations.

https://www.newscientist.com/article/mg20827824-900-men-beware-moving-country-could-affect-your-libido/

I think the Japanese population's lack of interest in sex has a lot to do with their super-urban lifestyle which allows for very little privacy. Combine that with the shame culture and there is a huge social barrier. Another indicator is that this is something that has affected this latest generation of both men and women.