It's troublesome and expensive to raise a family, but I get the impression that some people are running away from their responsibilities by choosing not to have children.
I think people are trying to focus on their careers. As a woman here, once you start a family you are not expected to do anything else. Working mothers are fairly uncommon in Japan.
Education costs a lot, and housing space is limited and expensive. If a working woman gets pregnant, they have to take time off work, which makes it hard for them to come back.
Many Japanese women feel that they want to go out and work, and try to advance their careers. My girlfriend works, and if she gets a good position and needs to focus on that, then we'll wait.
Raising children takes a lot of money. The Japanese economy is not as strong as it used to be, and so we don't have as many children as we did in the past.
The cost of living is so high in Japan that maybe parents here don't have the money to raise children. You have to have money and time to raise kids, and many people don't have both.