Regardless of whether or not young Japanese are afraid of sex, the Japanese population is dying off the same way it would in every country if they could control for immigration:
Economic development has an inverse relationship with number of children that a family has. Not just in Japan, almost everywhere. Both the US and Europe would have zero or negative growth if not for significant immigration, and that has nothing to do with 'cracking down on sex' or being afraid of it.
I agree with the reasons you presented, and I'm very aware of them already. And I didn't say it was the only or main reason, but do think it's part of the reason.
To have babies, you need to be having sex. Japan has among the lowest sexual frequency, among industrialized countries in the world. The lowest frequency among married couples, and in general, with frequency per week.
Many Japanese are simply not having normal sexual relationships. And for a significant number of males, the only sex they have is with prostitutes or masturbating with their hand. Prostitutes, their right hand, and sex toys are not out here having babies or marrying.
When you talk to many young Japanese women, a very odd mindset presents itself which will only make Japan's problems worse. Expect Japan's population to go into free fall downwards.
My opinion is however, anecdotal, but also based on years of living in Japan. And I can actually compare younger and older generations of Japanese a bit. Such negative attitudes towards sex wasn't present in Japan 15 years ago.
Japan's backwards ultra-conservatism, has in many ways created a climate of sexual oppression. Many younger Japanese women see being sexual liberal or open-minded, as being a prostitute for money or perversion. Many Japanese women think a guy walking up and having a simple conversation, is perverted or wrong. Often there is the 2 extremes, and not an understanding of the middle. In their minds, being the opposite of a prostitute is to be a 1950's style Cinderella fake virgin girl. Anything outside of missionary position is perverse.
If anything, you want to encourage female sexuality and support it, not oppress it. You want your women enjoying sex (and its many variations), male and female relationships, and babies in addition to their careers. Not for them to be lying about virginity work robots.
A police force that wastes taxpayer money on breaking into locked door member only private clubs and closed door hotel rooms to arrest consenting adults for having sex, speaks to ultra-conservative craziness and sexual oppression.
No police force in a democratic and free society, should ever be wasting people's time with preventing dancing after midnight or breaking down doors looking for group sex. And if they are, they are at war with basic human rights. Feeling good and naturally enjoying yourself, should never be the focus of a police crackdown, unless you live under Islamic Sharia law.
