The first, most blatant difference is that everything is written in Japanese. Depending on the circumstances, this can be a huge hindrance or not matter at all. For example, it isn't necessary to be able to read to figure out prices or to buy products like fruit or vegetables. Also, a lot of packages have pictures showing what's inside, or are foreign products to begin with (e.g. Pringles). Where I run into trouble is attempting to figure out whether packaged items contain any meat.
Japan is definitely a hard country in which to be vegetarian. (I've already met one JET who gave up vegetarianism here because it was simply too hard to maintain.) There is fish in practically everything. It's the base in most broths and is used as a garnish on otherwise safe dishes like tofu. There is also the unfortunate practice of hiding tiny shrimp under the cheese on pizza, so it isn't always visible until you bite into it. It often isn't considered "meat" to the Japanese, either, because it's not beef, so asking a native to identify something as "meatless" doesn't necessarily help.
There are plenty of differences completely unrelated to language. The first thing I noticed upon entering my local supermarket (Jusco) was the variety of shopping carts. There were the regular carts, the same as I would find in Meijer back home, but there were also smaller, slightly wedge-shaped carts. These, it turned out, are for carrying your handbasket.
It makes incredible sense. Not only am I a single person living alone (who never eats much anyway), I have storage facilities not far removed from the average dorm room. Even if I wanted to buy enough groceries in one trip to last me a week or two, I don't have the space in my refrigerator to store it all. (Except in winter, when my whole house doubles as a fridge.) Thus, the basket. Yet I am also the typical 90-pound weakling--okay, 100-pound weakling--and those bottles of soda or tea can get mighty heavy. Thus, the cart for the basket. It's one of my favorite aspects of the whole shopping experience.
The next thing that becomes immediately apparent is the size of everything--and this goes both ways. The produce section is at the front of the store, and I have never seen such monstrously large grapes or peaches in my life. (They probably got that way by vampirism against the watermelons and pumpkins, which rarely exceed the size of a volleyball at their best.) Rice, as well, comes in Extra Large Economy Size bags. I bought one my first day in Matsudai, and I'm not even halfway through it by now, six months later. The same is true of the bottles of soy sauce, for which there is a startling array of options.
For most everything else, small is the rule. Eggs come in sets of ten, rather than twelve--an interesting nod to the metric system. The largest drink bottles are 1.5L instead of 2L. Loaves of bread have a maximum of eight slices. Flour isn't available in bags larger than 1kg. Don't even think about finding a gallon-equivalent of milk...
Which brings me to dairy products. Or, rather, the serious lack thereof. When I left the States, I was accustomed to drinking at least a gallon of skim milk per week, in addition to hearty helpings of cheddar, mozzarella, parmesan, cream cheese, and cottage cheese. Now my dairy intake has dropped precipitously, and I barely finish a liter of milk in a month. The main reason is that it simply doesn't taste good.
I can't obtain skim milk anywhere in my vicinity--the closest I can manage is 1%--so unless it's diluted into coffee, tea, or chocolate, I can't stomach it. Cheese is particularly rare, with cheddar the worst of the lot. Camembert is highly popular to accompany drinks, as is "smoked" cheese, so those two kinds abound in bite-sized chunks for parties. Cream cheese is virtually identical to home, which really helps preserve my sanity. Parmesan is available in itty bitty shakers, another victim of the size differential. But cheddar, real cheddar, is the elusive pot of gold.
Along with size is the matter of packaging. "Wrapped in plastic" is a way of life here. Among the individually wrapped items I've come across are each cookie inside a bag, single ears of corn, clusters of six crackers in a box of Saltines, and party cheese bites. Half the time it's appalling how much plastic and foil wrapping I end up throwing away, but the other half it's absolutely necessary to keep food palatable in the high humidity. One of the side effects of this love affair with packaging is that cartons of eggs are sealed inside clear plastic, not opaque styrofoam. There's no need to open them to check for fractures.
Then, as with most things in Japan, there are the items that are *almost* the same as home, but altered just enough to be surprisingly foreign. The best example of this trait, for someone fresh from a degree program in potato breeding, is the variety of potato chips. (Of course, take it for granted that all the bags are small.) There are plain and barbeque chips available, but added to that are seaweed flavored, garlic flavored, octopus flavored, pickled plum flavored, and pepper flavored chips. (How does that tickle your taste buds?)
Another area with a wide variety is drinks. Coke products abound--Pepsi products are few and far between--though anything "diet" can be tough to track down. (The Japanese concept of "diet" appears to be the same as "not eating" rather than the American idea of strict nutritional intake guidelines.) Then there are about a million types of tea and coffee, with or without sugar and milk added, and tons of sports and health drinks (though generally lacking the bright artificial coloring of products like Gatorade).
Speaking of drinks, the custom of having tea or coffee is extremely widespread. The typical line to pick up a girl is, "You want to have tea?" As a customer at a service-oriented business such as a car dealership, I've been given tea or coffee to occupy me while I wait. (Imagine complimentary tea at Sears' Auto Service Center!) At parties, the most popular alternative to alcohol for those driving is Oolong tea. My personal favorite winter beverage is sweetened milk tea, nuked to within an inch of its life, for keeping warm.
I consider myself a reasonably flexible person when it comes to food, within the limits of vegetarianism, so I've been attempting to experiment with Japanese meals using the ingredients available. I have to admit, however, that the absence of seafood in my diet leaves me with relatively few options, and I don't find plain rice incredibly satisfying. I enjoy cooking, so I can make food to my own taste, but I invariably run into one major stumbling block. The hardest part of eating here is the nearly complete lack of any Mexican cuisine whatsoever.
Plenty of bread, crackers, and buns of all shapes and sizes, yet no tortillas. Red beans in everything from soup to candy, but no pinto beans. Corn on the cob, corn soup, corn sandwiches, and corn on pizza, but no masa or corn husks for tamales. Even salsa is a rarity. For someone who grew up on pinto beans, Mexican rice, and tortillas as main staples, their absence is unsettling to say the least. Christmas just isn't the same without enchiladas and tamales. And it isn't limited to the supermarkets--though there are plenty of American, Italian, and Chinese restaurants to supplement Japanese fare, I have yet to locate anything resembling Mexican anywhere near me.
Even when I can obtain the ingredients for cooking, the hazards don't end there. I still have to have the proper utensils and facilities for baking. The closest approximation to a rolling pin at Jusco is a plain wooden rod, which I quickly discovered is extremely susceptible to mildew. Trying to use a Japanese vegetable peeler (shaped like a tuning fork with the blade perpendicular between the arms) to peel potatoes earned me a nasty cut. It took me months to track down something as large as a standard 9" pie plate. (But that's okay, since my oven is barely big enough to hold it anyway.)
This is where I have to pause and put in a good word for Japanese desserts. It's chocolate heaven here. One lovely product is the instant chocolate cupcake--just add two tablespoons of milk, stir, and nuke for a minute and a half. Presto! Piping hot cup o' goodness. Also, it can be hard to tell the candy aisle from the toy department, because many types of candy double as merchandise for children's cartoons, coming with cute little figurines, plastic ornaments, pins, and other such accessories.
So, finally, I make it through to the checkout line with my purchases. As with everything else, I pay with cash. No one gives it a second thought if I hand over the equivalent of hundred-dollar bills, that's just normal. There generally aren't baggers. Instead, the person at the register adds one or two plastic bags to the basket, and when I get done paying, I move on to the separate bagging tables and pack everything away myself. Thus ends a typical trip to the grocery store.
There are numerous other kinds of shopping, of course. Buying magazines and comics, for example, is my favorite pastime. I haven't bought much in the way of clothes, but aside from having to switch into special shoes to enter the changing booths to try things on, it's mostly the same as the States--except that it's much easier to find clothes that fit someone as short as I am!