I'm working on my fourth year here. (including 1 seven years ago and about 3 in a row now)
One general comment I have is that the deeper you get into this the harder things get to pin down. While there is a strong sense of appropriate behavior and decorum at lot of what is a 'fact' to someone isn't that way to someone else. Foreigners looking for a specific way-for-something-to-be will often adopt an explaination someone gave to them once as a cardinal-rule and then insist that it's some kind of unwritten law.
If you want to roleplay in Japan you have to find your japan.
While I realize there aren't a lot of Japanese movies in the West you might do well to try to see some of Miyazaki Hayo's. He makes anime and has enough of a cult following to get his movies over to the states.
Try:
Mimi wo sumaseba (modern-ish life of a young girl -- the family is about as normal as they come)
Also for magic/mage in Japan the hesei tanuki kassen (about magical dogs who try to return Japan to the old way) and the recent Spirited Away would be good.
Three broad trends
Generational -- there are tremendous differences in peoples attitudes as you pass from generation to generation. Whole books have been written on the subject.
Grandparents are probably the most interesting. They live through a time of great suffering when the whole country went more than a little bit crazy. They've seen their country go from, effectively, a facist quasi-religious police state nominally ruled by a divine being, to an occupied country, to an economic gangbuster to a listless and battered titan. When they were young they probably met their spouse through an arranged marrage*, their grandchildren do much of their romancing through mobile phones.
The parent generation also saw tremendous change most (even near tokyo) grew up in the vestiges of a rural, agrarian system. They had five or six siblings, they were large familes and grew up during a time of opportunity and growth. Men sacrificed themselves on an altar of the company and women were exposed to the kinds of freedom their mothers never knew (and ran smack dab into a male establishment that was having nothing of it).
The younger generation really kind of fragmented. The sense of purpose their parents generation felt has largly disappated. Most are modivated by their hobbies and a desire to live a comfortable lifestyle. Young women still find their behavior strongly curtailed. Although I can't stand his writing I've got a few friends who think that Murakami's writing is evocative of this.
*=Despite common preconceptions the people to be married got to make the decision (though parents being parents they could exert influence on the person makeing the decision).
Regional
Most everybody has an accent/style of speach showing where they are from. Similar to britian (another island country where families have spent years and years in the same place) regional accents are common and strong. People from different regions also have markedly different behaviors and attitudes.
To my mind its a lot like England (which I have to admit I don't know much about). People have lived for a long time, like hundreds of years, in one place and developed strong accents and traditions as a result of that.
Generally people on the Kanto plain (basically Tokyo), are polite (cold) whie people out to the west (Kansai - i.e. Osaka, Kyoto) are more informal (aggressive). People in Osaka are sterotypically very funny. its kind of ard to explain they have this thing they call Tskomi and boke which is basically the funny guy and the straight man.
Each region, area and sometimes even village is different from the surroundings.
Socio-economic
[I don't agree with the previous poster who indicated that they beleive there is still a samurai and hinin class.
Samura -- my host grandmother was born to a samurai household in rural gunma (center of honshu). All this really meant was that she put that down on her school registration card. She felt the impact was minimal. The fact that her father was the town doctor was far more important (and this was pre-war).
Hinin -- I probably know more foreigners who know this word than young Japanese people (and most of those think of it in a historical context). There are still buraku around, but discrimination is kind of weird/limited. Basically the only way to tell a buraku from anyone else is to find out where they are from. If the area of the city or town is buraku then they're buraku. The only time I've heard this come up is during the "wedding background check".
Still you could have some kind of stronger discrimation in your game if you like.]
Socio-economic is important to talk about just because of how different it can be from western societies. In my experience educational background (i.e. what college you went to) is more important than social caste.
thullgrim said:
do they go to school year round with various small breaks or do they have a long summer vacation?
The big break in the school year is the end of tests... which is basically early January, into March. They get one month or so off in August.
thatdarncat said:
Thanks guys, that does help a lot 
Religion and beliefs - What are the major Japanese religions? Do they take holy days off? Do people go to a service every week or something like that?
I belevie that the official numbers are that 70% are shinto and 70% are Buhhdist.

Regligon in Japan is a funny thing. Most people beleive that their sincere emotions are more important than beleif in a specific doctrine. They focus strongly observance of family rituals related to dead relatives and shrines. Needless to say they aren't pushy about it. Most every family maintains some sort of small home temple with pictures of deceased relatives. Older people will often put a small offering of incense. (My host grandfather usually puts a small cup of coffee on his altar and prays for a minute once a day or so).
1% of the population is Christian. Most of them aren't significanlty different in behavior toward relgion than other Japanese people. I only know my landlord is Christan because he mentioned helping to build a church with his congregation.
There is a more crusading brand of christan of course. I know a few people who are put off by Christans because of the number of times they've been accosted on the way to work by people demanding if they beleive in god. During Christmas (and maybe easter?) there are people standing around on street courners with tape-recorders-attached-to-bullhorns patiently explaining basic doctrine to people hustling around.
(There are probably a lot of celestial chorus opportuniites. Japan was very responcible to Christian belieifs when they were introduced initially now there is little intrest however).
thatdarncat said:
-Chan -kun and such. When are they used and what's the ettiquite about using someone's family and given name? I know that names are given Last name First name, and I think using someone's first name implies friendship - you wouldn't use someone you'd just met's first name, you'd wait until they told you that you could?
This is one of those things that doesn't really operate strictly by the rules. You never tell someone they can use these terms with you really.
I'm male and my host family used to call me chan when I lived with them. (Gura-chan, actually). The boss of my office calls every male there -kun. Among their friends most people have a name they are commonly called but its kind of up to them.
One circle of friends has kenji (his first name), Nagi (the last two characters of his last name kusanagi), and Oku-chan (his last name plys chan).
Women do tend to use lower names (personal names) more than men. Though a few people switch around at random.
People will spontantously make up nicknames as well. Two women in my office used to call each other lastname-chi. I asked around and 1. nobody could explain it 2. they started calling me Gurafu-chi.
Generally everybody does last names unless you are being introduced in a friendly setting.
People also use titles contantly to refer to people (unless it would be confusing)
On other comments about mixing gender.... in general you don't need to do anything like use-chan-to-imply-a-he-is-a-she to start a fight. You just take an obnoxious tone of voice and change your speach pattern and *viola* you're having a fight. Except when people are drinking this doesn't happen. The whole getting-into-a-fight-with-someone-and-having-a-verbal-sparring-match doesn't happen much. I've never seen Japanese people start yelling about each others mothers or implying ridiculous things. Just showing that you're mad at someone feels the same to me as launching into a curse fest in english.
Xeriar said:
In downtown Tokyo there are even 'sleep cell hotels' or whatever, which is basically a safe just big enough for a human to sleep in comfortably, with TV.
I know of precisely three of these in Tokyo. They're an exception moree than the norm. Since you can travel just about anywhere in the country in a few hours most business trips are a day or two days.
Foreigners love them though. I've known a few people to stay in them just for the experience.
Xeriar said:
Though they work many hours overtime, they also take what could be considered a rude number of sick days (more than any other country IIRC) putting there average productivity below America's, even.
The lots of overtime thing is a bit misleading. There are a lot of people who feel like work is home. People will often stay late until the last person is done and then go drinking.
The sick days thing depends very much on the person. We had one slacker at work who did this a bunch and it was a real issue. I think you've confused national holidays (just about one a month baby!). Most of the guys I know at work take off a few sick days a year.
Japanese people do sometimes receive a really large number of sick/vacation days (depending on the industry). I work in finance and I took all of mine the first year and the personnel department explained to me that people get all those days in the event of some sort of emergency they can take off without the company docking them pay.
Xeriar said:
Sometimes the male of the household breaks from this pressure, and leaves his family in shame, there is an entire district of Tokyo where these people reside, it's rather sad.
Uhhh.... where did you hear this?
(People do leave their families of course, but usually its for the normal kind of I-hate-my-wife/I-want-to-move-in-with-my-mistress kind of stuff. The wives usually move back in with their parents if they can, not to some sort of strange abandoned-wife-ghetto.)
Last comment (about money)
After years deflation (and strong inflaction elsewhere) -living- in Tokyo, like Japanese do, is about the same as compairible locations (NY or London).
Personally I grew up in NY (and my folks still live there) an dI live in Tokyo now and I think it's about the same, or if you're willing to slum, slightly cheaper in Tokyo.
Deflation is really crushing the market and costs for essiential goods have continued to fall. Customers -can't- spend more money on things so companies that raise prices see a preciptious fall of in sales.
The plaecs that are doing well (like Matsuya foods which operates the Matsuya beef-bowl joins) are focusing on getting cheap materials from China.
Untill recenlty there were a few places which were doing better (like Starbucks -- where you're basically buying caffine and a chance to sit down) but even they have started to miss earnings targets and revise forcasts downward in the last year or two.
[sorry if some of this is unclear, the post got lost once and I don't really have time to go through and fix the grammar.]