I think work expectations and schooling play a bigger role in that than the city planning, but it may also be suffering from it's own success in some ways. An abundance of choice can sometimes make commitment difficult, dating apps are one example. It's easy to stay non-commited to a social regulationship when it feels like they are a dime a dozen.

I also get the impression that a lot is expected of individuals in their social performances, and so for those who struggle to participate, there isn't as much support.

This is exactly it. People are very busy with work, and work too much, and then there's so much choice socially, so they end up making plans for their free time several weeks in advance.

Just wanted to throw this in: https://ourworldindata.org/grapher/annual-working-hours-per-... because recently I was talking to some friends and they were very much under the stereotype that in Japan you work some horrendous amount of hours - that is not true. IIRC data is both self reported and from companies.

The real reason is the same in Japan as it is in Europe and America: even controlling for hours worked, low wages, high cost of living, and other economic costs associated with having a child, women are choosing not the have children because it would require them to end their careers in their prime. It is extremely difficult to have a child and a career at the same time as a woman, and many never return to the workforce. Even women who make good money and can afford to have children decide not to because it would require them to stop working