Note: The contents of this page are based mainly on my own experience, which is some cases is pretty limited. Please let me know, using the link at the bottom of the page, if there's anything you find to be incorrect.
THINGS THAT ARE EXPENSIVE/DIFFICULT TO BUY IN JAPAN
Many of these things can be obtained from imported goods shops in major cities, such as Sony Plaza, but there may not be one near you, and even if there is, the choice will be a lot more limited than at home and the prices will be higher.
Toiletries are pretty expensive in Japan, even if you buy the local stuff rather than insisting on your favourite brands from home.
You can get deodorant, you can even buy pads to protect your clothes from armpit sweat, but you can't get anything that actually prevents you from sweating in the first place. And believe me, if you're here in summer then you'll need it!
Most Japanese toothpaste doesn't contain fluoride, so if you want fluoride then bring your own toothpaste - especially if you need stuff for sensitive teeth.
- if you're a shower gel kind of person. You can get "body soap" and there's a huge selection of shampoos and conditioners, but you'll be hard pushed to find a bottle of shower gel for less than ¥800.
Not a major issue for me personally, since I wear very little of the stuff, but I'm told that make-up is expensive here. Having said that, they do have quite a wide range in a lot of the 100 yen shops!
Obviously you don't want to be wasting your limited luggage allowance on food, but there may be certain things that you miss.
The Japanese have plenty of sweets, but most of them are of the boiled variety. They're sometimes flavoured with red bean paste (anko) or green tea (matcha), which can take some getting used to! Chewy sweets, such as toffee (caramel), are less easy to get hold of, but they do exist.
As for chocolate, the local stuff is quite rich in terms of cocoa content, but you may not be too impressed with it if you like your chocolate creamy. I like the Japanese stuff, but I did miss Galaxy! (You can get Dairy Milk in Sony Plaza, but not Galaxy.) There's not much to choose between the different brands, in my opinion, and it all comes in pathetically small bars; it's hard to find a single bar bigger than 50g.
Baked beans, Marmite
As far as I'm aware it's just not possible to buy these in Japan.
PG Tips, Tetleys, etc.
Unusually for a Brit, I'm not a tea drinker myself, so this wasn't something that I picked up on; however, a visitor to my site tells me that "black teas available in Japan are usually weak with poor flavour", so you're advised to bring a supply of your favourite brand if you can.
Electronics in Japan are pretty advanced, but in my (albeit limited) experience most things aren't especially cheap. Bear in mind that the mains supply here is only 100V, with a frequency of 50Hz in eastern Japan and 60Hz in western Japan. The line is drawn along the Ooi river in Shizuoka, east of Nagoya.
Mains plug adapters
If you're coming from North America then a bit of rooting around the electronics shops in the major cities should turn up an adapter or two. However, it's a lot less easy to find adapters for appliances with European - and especially British - plugs. Far better to buy them before you leave. The ones that say they are for North America and "some Asian countries" are fine. The Japanese plug is basically the same as a US plug but with no earth pin.
If you want to get online in Japan, and you have sufficient funds for the necessary outlay, then it's probably a good idea to bring a laptop with you. As laptops are designed for international portability, it shouldn't have any trouble coping with the 100V, 50/60Hz supply in Japan. However, you may have difficulty getting suitable power supplies for any peripherals you bring with you, unless they get their power via the PC. If you have a modem, make sure that it has a US-style telephone connector. It's very difficult to find an adapter for a European connector, and the only alternative is to rewire the thing yourself. Again, best to buy before you go. Click here for further information on getting online in Japan.
Medical supplies tend to be expensive in Japan. It's normally fine to import prescription drugs, although "in principle" you're only allowed to bring one month's supply into the country and it's a good idea to have a doctor's note just in case any questions are raised. Most over-the-counter drugs are fine too, but not all!
Up until recently the only version of the pill available in Japan was a high-dosage type, strictly for the regulation of severe menstrual problems. However, in 1999 the contraceptive pill was legalised in Japan, and is now available from some pharmacies. (About time too - it only took them a matter of weeks to approve the use of Viagra!) I'm told that it's very expensive, though - and national health insurance doesn't cover preventative medicine so I don't think contraception is covered - so it's a good idea to bring your own supply if possible. Talk to your doctor and see if he/she will give you a year's prescription in one go. They're not supposed to (in the UK at least), but if you explain your situation, and have been using the same brand for a while with no problems, then they might do.
Cold and 'flu remedies
Available in Japan, but expensive. But be careful what you import; stimulants such as pseudoephedrine, found in Sudafed, are illegal in Japan! Bring plenty of paracetamol/aspirin. Anything you bring in should be in unopened packets, to avoid any awkward questions.
I've had conflicting reports on the usefulness of Japanese ones. AIDS seems to be a taboo subject in Japan, but this does not mean that it doesn't exist. I was originally told (several years ago now, by a male Westerner living in Japan) that "Japanese condoms are famously unreliable and too small for Western men". However, more recent visitors to my site assure me that "Japanese condoms are really the standard of the industry world wide; the quality of most Japanese brands is top notch and they export to all parts of the world"... so I suggest you do a search and make your own judgement!
Big clothes and shoes
Basically, for both clothes and shoes, average size in the West is towards the large end of the scale in Japan. In UK sizes, if you're over about shoe size 6½ (women) or 9/10-ish (men) then you may have difficulty getting shoes to fit. Japanese shoe sizes are normally measured in centimetres, which makes more sense than the arbitrary sizes we use elsewhere; all you have to do is measure the length of your foot! My UK size 6½ equates to 24.5 or 25cm in Japan. Slippers and sandals often come in S, M, L and sometimes LL. In women's clothes, a UK size 10 seems to be roughly equivalent to a Japanese size 11.
Summers in Japan are very hot and humid - in central/western Honshu the daily high is over 30°C most days in July and August, and it doesn't drop below about 26°C even at night. Even up in Hokkaido it's pretty warm. From early June until mid-July is the rainy season, but it's far too hot for a raincoat, and you can get umbrellas from ¥100 upwards. Winters can be cold, especially in the north, and most Japanese apartments might as well be tents as far as insulation is concerned. So dress accordingly! However, you can buy warm clothes quite cheaply in Japan if you shop around - for example a fleece or a thermal vest for about ¥1000. You'll probably want to send/bring a few things from home but it might be just as cheap to buy most things new once you arrive.
Before I came to Japan I read that it was difficult to get a bra in a cup size bigger than B. This is not true; larger cup sizes are available, although you'd probably be struggling if you're bigger than a D-cup. However, I suspect that the number part of the size is more limited - e.g. what would be a 38B in the UK might be hard to find here (and would be in metric measurements anyway). Also, every bra I've seen on sale seems to have semi-rigid shaped cups, all padded to a greater or lesser degree. It seems that Japanese women like their underwear to give their figures a helping hand!
There's plenty of sunblock available, the factors ranging from 30 to over 100, but it's very expensive and you will very rarely see anything with a factor lower than 30.
- if you're going to be in Japan in the summer. To be honest I haven't checked the availability of this, but no doubt it will be expensive in Japan - if it's available at all - and I thought it was worth metioning since as I write this my legs are covered in mosquito bites! There's an antihistamine cream you can buy called Muhi S to treat the bites once you've got them (apply frequently!), and that's not too expensive, but of course prevention is better than cure!
You'll have no problem buying towels in Japan, but if you're staying in Japanese hotels, ryokan etc. then you'll probably find the towels supplied (if there are any) a bit on the small side.
Hot water bottles
It's not difficult to find hot water bottles here, but they're not like the soft rubber/fluffy ones we have in Britain. They're made of hard plastic or aluminium and resemble legless turtles. Cuddling up to a turtle just isn't the same... However, a helpful visitor to my site has told me that you can get something called "mizu makura" (water pillows) in Japanese chemists'. These are very similar to our hot water bottles, but are normally filled with cold water to soothe a fever.
International driving permit
The chances are that your driving licence will not automatically entitle you to drive in Japan, but if you get an IDP before you go then that will cover you for a year. (It won't cover you for motorcycles - even 50cc scooters - unless you have a proper motorcycle licence though.) In the UK, IDPs are available from some post offices and cost about £5.
If you're in an urban or suburban area then in most cases a car will be more hassle than it's worth; no harm in getting an IDP just in case, but you probably won't have much call for it. If, on the other hand, you're out in deepest inaka (countryside) then you might find a car to be a life-saver. Living 40 minutes by bike from the nearest station, and another 30 minutes by train from the nearest shop bigger than a 7-11, might be very good for your Japanese but it probably won't do much for your sanity!
THINGS YOU'LL WISH YOU HADN'T BOTHERED BRINGING
Japanese FM radio uses lower frequencies than we do (in Europe, at least). The range on a Japanese radio goes from roughly 75MHz to the low 90s. Japanese radio is mostly pretty dire anyway. A short-wave radio may be worth bringing, but whether it will be any use probably depends on your location. I brought one, but all I can get on it in Hikone is two AM stations. (I can also get two FM stations on my Japanese radio.)
Anything that gets its power supply via the computer should be OK, but anything that you have to plug into the mains is liable to present problems. I've seen mains power converters for up to 12V DC, 300mA, but it may take you a while to find what you need. I gave up trying to find one for my 15V hand-held scanner, after being told by several shops - and finally by Logitech themselves - that no suitable converter exists.
If you're coming from North America, with its weedy 110V supply, then you probably won't notice much difference when you plug your hairdryer into a Japanese socket. However, a European hairdryer will be reduced to less than half its normal power.
As mentioned above, prescription and most over-the-counter drugs are fine. However, the Japanese take a very dim view of the possession of illegal drugs, and if you are caught with even just a small amount of marijuana then you are liable to be deported. I'm told that in Japan there is very little distinction between "soft" drugs such as marijuana and "hard" drugs such as heroin. Anything that's illegal is a big no-no.
Japan uses the NTSC system, so American videos are fine, but European ones (PAL system) won't play here unless you get a clever, and accordingly expensive, video machine that can cope with both types. You can get them converted though, which costs from about ¥1500 upwards.
In Japan, you don't need a sleeping bag unless you're camping (and finding a place to pitch your tent isn't as easy as you might think) or staying with a friend who doesn't have enough extra bedding. A cotton sheet sleeping bag might be useful in some situations, for example youth hostelling. Some youth hostels will charge you a little extra (¥100-200) to hire one, but others include the bedding charge in their overnight fee, so unless you're planning on doing a lot of hostelling, even a sheet sleeping bag may not be worth bothering with.
THINGS THAT ARE AVAILABLE SURPRISINGLY EASILY/CHEAPLY