Knowing then what you know now

I am interested to pique the brains of foreign residents who have been living in Japan for quite sometime. If applicable, could you share your life in Japan learnings/gotchas/wisdom that you wished you knew when you arrived, based on what you know now. The mistakes/things the "newbies" do/forget. In an attempt to make things a tad less vague, consider the use cases when dealing with Government/Financial institutions.

I know that new foreign residents need to register their address within 14 days (or asap afterwards) after arrival at the local city hall, join the national health system (either via the employment scheme or the national health insurance).

Is there anything else?

Might not be what you are looking for, but I recall the circular problems I had when opening a bank account and getting a sim card for my phone. The lessons I learned from that were:
- They could explain things much more simply (i.e., rather than saying you need a phone number, you need your own mobile phone number to open a bank account, an IP number or land-line number were not sufficient - why didn`t Shinsei say that in the first place),
- If they tell you one thing, it`s probably wrong. Like the BicCamera guy saying I needed a phone number for a contract when the point of my being in the store was to get a phone number. After 30 minutes of round and round arguing, he checked with someone and "you don`t need a phone number for the contract", and I got my sim card, and number and trotted back to Shinsei and got my account.
- Also with banks (a different one, for my company), they will lie to you - point blank. "Yes we have sent your debit cards to your office" when in fact they were on the guy`s desk for six weeks.

Probably the other footnote is that the post people don`t always use my mailbox for my mail. When my cash-card finally turned up, they used a slot on my front door for the delivery failure notice (which I had never used). Another phone call to the bank and it was re-issued.

Thank you for sharing, JapanCustomTours. Everything is interesting to me.

Similar questions have been asked by people of all ages and nationality for decades, but the answer all depends on the era, region, your age/status, and from where you're coming to where.

I mean, I'm not a "foreigner" per se here in Yokohama, Japan, but it's been more than 4 decades since I returned to Japan from LA (which was a huge culture gap on its own), and I'm still suffering culture gaps (like every other local), because values and technology and policies keep changing all the time. Plus, at this point of my life, there are still things I never had recognized.

For example, it was just a few weeks ago that I thought the huge renovation/repair in our house was finally done when we noticed that the mirror in our shower room reflects everything in our bodies except the heads. I can see every bit of me, but when the taller men of my family stood up, like they always do when taking a shower, they couldn't see their heads in the mirror.

We realize that (although showers here are a post-'70s Western thing) the majority of people in Japan sit when they use the shower even at home (while we realize that shower rooms in LA don't have mirrors, just as they don't in many countries). The men in my family had considered themselves as average Japanese citizens who had never lived abroad, but I guess there's a first time for everybody.

On a related note, me and my folks visited LA recently for the first time in decades and were met for the first time with cars you don't stick a key into, and gas stations where you do everything by yourself. Oh, I also encountered a DIY cash register for the first time in London. Soon, Yokohama caught up on everything.

it is highly unlikely that you, a spouse of Japanese national, can get troubles with miscellaneous paperwork, if you do it with her.

Thank you everyone for your thoughts!