
I can’t speak or read a word of Japanese, will I be fine? Or: common worries that disappear pretty fast
In Tokyo you will. In Osaka and Kyoto, probably too. In other more rural areas, it may not be as easy.
As you probably know, Japanese writing system is a tad complicated, with its 2 sets of syllables and the use of Chinese ideograms. In major tourist areas however, almost all signs will be transliterated into our alphabet. In many restaurants, window displays are full of plastic imitations of your dishes so you can just point!
In the suburbs or the countryside however, a lot of places will use only Chinese characters, which are always tricky even to the basic speaker, but the overwhelming majority of Japanese people, from station attendants to passers-by, will do their best to help you find what you need. With lots of mime and pointing. Although this is slowly changing, most Japanese people do not speak great English, or if they did when they were a student, they forgot most of it.
I’m bringing my cellphone, right?
Nope. Wavelengths are not compatible. Phone booths are still in use all over the country (purchase cards at the airport or in combinis like 7 eleven) If you cannot spend your vacation without a cellphone, you can rent one at the airport.

What am I forgetting?
You are most likely bigger than the average Japanese person in several dimensions. You probably thought of shoes, pants, bras, but have you thought of condoms? If you buy Japanese condoms you’re probably in for an ego boost but not for a safe experience. Also bring your medication: Japanese people being lighter, dosages can be quite different.
If you are planning on meeting with Japanese hosts, it is customary to bring little gifts that are typical from your country. Nothing fancy like a bottle of wine, more like souvenir magnets, key chains or typical candy… something inexpensive, so that your hosts could return the favor easily, but that couldn’t be found in Japan.

Earthquakes, what’s up with that?
Well, there are some. A lot of them, actually. They’re fun the first couple times. Check them out daily here:
http://www.jma.go.jp/en/quake/
Luckily the Japanese are well prepared for earthquakes. Buildings are much more seismic safe than anywhere else in the world, and in risk areas the majority of construction materials are light (they use a lot of wood and paper. Seriously, if you walk in front of a house in construction you’ll see they build them with staplers).
It is unlikely that a major earthquake will happen during your stay, but just in case: protect you nape and head, move away from windows and sit under a sturdy piece of furniture or in a small room where nothing can fall on you (toilet or futon cabinet!) Standing in a doorway is only useful with bearing walls; don’t try it in those cardboard houses. The highest danger is not the quake itself, but the potential ensuing fires. Gas comes with quake sensitive circuit breakers and should get cut automatically, but be on the lookout for leaks and smoke.
Don’t let Mother Nature’s small quirks ruin your stay; it will most likely be over before you can remember any of this advice.