First, a quick note on “culture shock”. I understand how you’re using it - you’re referring to the aspect of Japanese culture that most shocked or surprised me. However that isn’t what culture shock is really like.
Real culture shock is a hundred little things that make you feel like you’re walking down a flight of stairs and missed a couple of steps and are now staggering forward down an endless flight of stairs struggling to maintain your balance. It is walking through a quiet Japanese village at 5am in the morning watching the sunrise with a feeling that soon people will begin to wake up and the surreal experience that is life in a completely foreign country will begin again. It isn’t “Oh, that’s surprising!”, but rather an ongoing experience that comes in waves even a decade later.
Okay, back to your question. Here are my top 3:
1. Being Illiterate - I read compulsively. I read everything. I had a habit which used to irritate my colleagues back home, which was being able to read whatever was on their desks in seconds, even if it was upside down. … and then I came to Japan and I stood there in a supermarket trying to read the label on something, sounding it out like a 5-year-old learning to read, and feeling like a prize idiot when I realised it was “cream” (kuri-mu). I wasn’t alone - I know someone who bought a bottle of what they thought was juice (it had pictures of plants and stuff on it!) and only realised it was oil when they took a mouthful. You’re surrounded by signs you can’t read, and your ignorance pounds at you every moment of every day, and even decades later I still occassionally make amusing mistakes.
2. Being Foreign - In Japan less than 1% of the population are foreigners, and most of them are Asians who blend in pretty easily. There’s nothing that reminds you that you’re a foreigner more than some little kid pointing excitedly and saying, “Gaijin da!”… or some high schooler whispering it to their friends… or some curious granny trying to peek into your shopping basket to see what the foreigner eats! That sense of “otherness” is part of what exaggerates the culture shock in Japan.
3. No Frame of Reference - That example of missing a step I opened with? That’s pretty much life in Japan. You’re walking along thinking you’re fitting in nicely, and then you make a mistake a child wouldn’t make. Maybe you walk into a tatami room wearing shoes, or forget to bow to someone important, or use an unfamiliar gesture and only realise it when everyone looks confused. Of course it isn’t a one-sided thing. One of my students once ran up to me and asked loudly, “Am I sexy-cute?”. I was appalled - teachers do not call their students “sexy” under any circumstances! She was devestated by my lack of affirmation of her cuteness, I was stunned by her question, and my colleague was trying her best not to laugh at my discomfort. Other times it is more subtle, like colleagues trying their best to “be Western” (or what they think is “Western”) to make you feel at home. I had a colleague who used to try and hug me. I just stood there like a statue being hugged, not knowing what to do. I then explained that not all Westerners are huggers (only my closest friends who I have known for many years can hug me uninvited).
Overall I’d say that 90% of Japanese culture is the same as everywhere else. Yes, they sell coffee in cans, and I’ve even seen one of the famed panty vending machines (I also saw one selling Hello Kitty “massagers), but these aren’t the things that cause culture shock - it is the unexpected little things that make you feel stupid and foreign that cause the biggest culture shock.
As a closing note, and for the sake of balance, I should note that Japan is a wonderful place to live. I can go to sleep without locking my door, the trains run like clockwork, and the longest I’ve ever waited in a hospital was an hour (and that was when I came in at 4am in the morning with an emergency and they had to wake the doctor). Your greatest fear will probably be walking into a tatami room wearing shoes or random co-workers trying to hug you.
P.S. I have just remembered my first day on the job when I walked in and was asked to judge a contest at the school “cultural festival”. At first I thought it was a fashion show as one girl walked onto the stage modelling a beautiful gown. Then a growing sense of “something is not right” as the next contestant walked up in her school uniform and flashed her panties. The next contestant, in a sexy nurse’s uniform was the clincher… she hadn’t even bothered to shave her legs… wait, did I say “she”? I meant he. He. It was a cross-dressing show and I was the only one not in on the joke. The worst part was when the nurse, angry at his low score came over and tried to “induce” me to give him a higher score. Rudolf the red-nosed reindeer had nothing on me as I blushed bright red while trying to maintain my dignity and my hold on the scorecards as an angry cross-dressing high school student tried to wrestle them from my hands.
A healthy sense of humour and an ability to laugh at yourself are probably the best antidotes to culture shock.