One more drawback to mention (Having lived in Tokyo a few years) it’s worth pointing out its not exactly kid friendly. I really don’t think most big cities are tbh.
The only thing I like better about where we live now is the much higher salary (even with cost of living) and the access to outdoor activities. You'd have to take a train at least an 1.5 hours away to get to larger green spaces in Tokyo. Arguably, this might be more convenient for those that don't like driving but getting several kids ready and babysitting them on a long train ride is a bit difficult.
Boarding public transit is definitely an issue. Going anywhere with small children is a bit difficult to be honest as their are quite a lot of rules. For example, no toys in the pool.
Constrained and limited places to play outside. Outside of the park everything is concrete and many types of play are banned. When out, I had to watch them like a hawk. Here they go over to a neighbors yard to play and have no such worries.
Childcare is also expensive to get if both parents do not work (in that case it’s free).
That said I knew plenty of expats from population dense areas that were of different opinion. They had cars too :)
I used to like living in the city with a kid. Lots of access to interesting places and activities, able to walk to school and playgrounds and such. It’s lost some allure during the pandemic.
Many places were shut on and off due restrictions during our time. Definitely makes thing harder.