When I visited it seemed true: lots of rather young kids walking around the streets on their own, tons of tiny mixed use roads for kids to freely and safely walk around in, etc. Heck, culturally they even have that Kid Tasks[1] show. It seemed a lot better for kids than NYC (where I live now), Silicon Valley (where I used to live), or small suburban towns in the south (where I grew up).
I'm also surprised you lived in a lived in a high-rise, famously uncharacteristic of Tokyo housing, which may imply you lived in a less family friendly district than the typical Tokyo resident.
[1] http://www.cbsnews.com/news/japanese-young-children-solo-com... [2] https://www.youtube.com/watch?v=e5k5XTZy0rA
And yeah, I lived in Shinjuku 5 minutes walking from the largest subway in the world in terms of people going through and it and physical size. It was a busy area.
This is the apartment I lived in - https://tokyoapartmentinc.com/room/17207/
http://www.rental-apartment-tokyo.com/?post_type=fudo&p=2036...
I never felt like an outsider at all, that wasn't an issue. The issue was that you have to make a daily effort to get your kids outside whereas in the suburbs here in Seattle, they can just go outside when they want. That's not an issue once your kids get older, but at 5 and 6 it's a little early to let them run around Shinjuku. It would have been easier if we lived outside the Tokyo center.
The dark is a real thing. It is not just the rain. It's more the large number of overcast days plus the very short days during winter months.
Whether or not it bothers you is a different matter. As far as I can tell, it's practically a biological thing. The lack of light just gets under some people's skin while others aren't bothered by it. Ask yourself, do you find gloomy days draining: oppressive clouds looming overhead, color washed out of everything, can't go outside, cold, wet? Or do you find them energizing: turbulent sky looking different every day, you snuggly in the warm light inside, doing creative stuff on a rainy day at home, or bundling up and getting refreshed by the cool breeze and rain spray?
If you're more the former, Seattle will suck your soul out and drown it in Puget Sound. If the latter, you'll love it.
Personally, it's a great fit for me. I love the contrast in weather between the summer and winter months. When it's miserable out, I love nothing more than settling in under warm lamplight and reading or coding. I can't imagine living somewhere arid. I would dry out like a frog on a hot windshield.
If you're considering moving here, I would suggest renting for a year. If you make it a full 12 months and don't feel oppressed by the climate at all, you should be fine.
The winter is Seattle is best spent hopping from coffee shop to coffee shop and getting snug with blankets.
Surely there's indoor swimming pools you can go to. In that climate, it seems to be stupid to even bother building an outdoor swimming pool.
Of course, if you're talking about the ocean/sound, there's not much you can do there, but I never hear people in the Northeast complaining about it rarely being warm enough to swim at the beach. I doubt the water's ever warm in Maine either.
Not to mention, we had a 750 sqft, 2 bedroom apartment that cost $3,000 a month. It was a quality of life downgrade compared to living in the Seattle suburbs.