Japan is a group of volcanic islands situated east of Korea. Home to the samurai (an approximate equivalent of the European knight). Most of the landmass (approximately 80%) is mountainous and unsuitale for farming or residenmtial uses.
Brief Japanese History
The Heian Period
The Heian Period lasted from 795 to 1185, and is generally considered to be the height or Golden Age of Japanese Literature. The most famous book of the time, the Tale of Genji by Murasaki came from this period, as did the Pillowbook of Sei Shonagon; these were some of the first novels to be in the formal Japanese written language, as opposed to earlier books which were written largely in Chinese.
During this time the Emperor commanded the country as ruler, and the court Aristocracy were at the height of their power; they would never again be this powerful. If you are interested in playing a persona from this period, picking names from the Kuge (the court aristocracy) is appropriate; picking a Buke ('samurai', see later) name is not, as they did not exist.
Muromachi Bakufu/Hojo Shogunate
This period lasted from 1185 until the Imperial Restoration by the Emperor Go-Daigo in 1333. The period began when, in 1185, Minamoto Yoritomo was declared Shogun by the Emperor at sword point, and was effectively the ruler of Japan. Shogun was a prior title which literally meaned nothing more than 'Barbarian subduing Generalissimo'; but after Minamoto Yoritomo claimed the title it became the Supreme Military dictator.
Yoritomo founded the Muromachi bakufu (lit. 'tent government'), so-called because of where they set up the Shogunate government (muromachi). When Yoritomo died the title of Shogun passed to the clan that had adopted him, the Hojo clan, who ruled until they were cast off.
Ashikaga Shogunate through the Onin War
In 1333 the Emperor Go-Daigo decided that he wished to claim the power for himself and, after returning from an exile, enlisted the help of Ashikaga Takauji, who threw his support behind the Emperor. When they succeeded, Takauji expected to be named Shogun, but Go-Daigo was understandably concerned about giving supreme military power to someone when he had just shaken off the same thing. Takauji, affronted, turned on his master and succeeded in conquering half of the country. The other half would hold out for several years (North and South Japan each had an Imperial Court) before being tricked in to coming to Takauji's court and getting consumed.
The Ashikaga shogunate would technically last until the Tokugawa Shogunate, its' power to rule the country was broken in 1467 by the onset of the Onin war. The Onin War was a succession dispute for the Shogun that was used as a front for two warring families to go at it like pitbulls. They each backed a different candidate for Shogun, and beat the tar out of each other. It is important to note that at a time when in Western Europe a large army was 3000 men, during one of the battles of the Onin War one side had 70,000 people...and the other had 80,000.
The war, which lasted until 1477, crippled the power of the Shogunate and launched a new era of feudal lords vying for power and the seat of Shogun.
The Sengoku/Period of the Nation at War
The next 133 years were a period of near constant and total warfare as people jockeyed for power, but in the end of the Japanese Warring States period three men came to the forefront. The first was Oda Nobunaga, who was largely regarded as a butcher. During one particularly brutal slaughter it is said that he had 40,000 monks and nuns put to the sword over a weekend. In the end Nobunaga was betrayed by one of his generals, and committed suicide in order to escape a death by torture.
He was succeeded by his general Toyotomi Hideyoshi a former peasant who had risen from the rank of Sandal Carrier to General. Through diplomacy he managed to convince Nobunaga's army to stay togethere where normally it would have fallen apart to infighting. With this army he managed to largely unify the country, but he couldn't convince any if the Shogun families (Hojo or Ashikaga) to adopt him. Since he was born a peasant, this meant he couldn't be Shogun; he took the title of Regent, and then when his son was born took the title of Taiko (retired regent) so that his son could be ruler when he was old enough.
Toyotomi had three major problems in his reign. The first was the first invasion of Korea, which failed. The second was the second invasion of Korea, which failed just as miserably. And the third problem was that he had his son too late in his reign; when he died, the boy was only an infant. Toyotomi did the best he could in order to try to preserve his son's reign by creating a Council of Regents in order to watch over the country until his son was old enoigh. And then he stocked the Council with political enemies such as Mitsunari Ishida, and Tokugawa Ieyasu.
Several years in to it, however, things came to a head, and Ieyasu was put in the position of essentially having to rebel and take over--which is likely what he had been waiting for. Modern academics believe that Ieyasu may not have been quite as tactically brilliant as the previous two men, although he was more so than Ishida, but he had significantly more patience then either of his predecessors. And so, in 1600 (baaarely period), Ishida's Army of the West and Ieyasu's Arm of the East clashed at Sekigahara, where Tokugawa Ieyasu won and became the Shogun. Woot.
Misconceptions on Samurai
The first misconception is that the Samurai existed for thousands of years. This is completly and patently untrue. Essentially the Samurai existed from 1591 and Toyotomi's Sword Hunt and acts banning social mobility and removing the tradition of ji-samurai (warriors that fought during war, and worked as farmers during the rest of the year). So while Samurai are period, just barely, the Samurai that we think of when we watch Kurosawa films only existed for a few years in period. While there were proto-samurai before that, there was much more social mobility, and the Golden Age of the Samurai didn't exist until out of period.
Second biggest misconception is that the Samurai Sword (Katana) could cut through anything, never broke, and were basically the best swords in the world. While I do prefer them to European swords personally, they could break, they couldn't cut through anything, and they were not the super uber sword everyone likes to think they are. People were gifted with swords from their Lord, and obviously if you have more then one son both of them can't have your three hundred year old ancestral sword, because the King Solomon trick just doesn't work.
Third misconception is the 'Samurai Worship' thing that seems to go around, believing that all Samurai were avid followers of Bushido and didn't ever do anything wrong Just like not all European knights were bastions of chivalry, some Samurai were downright bastards. Greedy, angry, bitter Samurai did exist, as did Samurai who wanted nothing more then to have lots of sex and own all the best in life, spurning the minimalist ideals and rejection of material goods that Buddhism teaches us.
Another misconception is what exactly it means to be Samurai. Samurai, literally, means 'to serve' and it is a social class. Someone who fights is called a Bushi; all Bushi are Samurai, but not all Samurai are Bushi. There were Samurai beaurocrats, Samurai Ladies-in-waiting and Samurai who had absolutly no talent for the art of warefare and did not want to die. So you can be Samurai and not fight, I promise, which is the major distinction between a Samurai and a historical Knight. Also, calling yourself a 'Knight' in the society is a bad thing if you aren't, because people are going to get pissed; Knight is an earned title in the society. Calling yourself a Samurai is fine, because that is just calling yourself a Nobleman/Noblewoman since it is a social class.
The final misconception is directly related to the SCA. That is that it is Difficult, Impossible, or Wrong to play a Japanese persona in the SCA--after all, we are a European organization. Wrong, so very wrong. First, it is not more difficult to play any persona more then others; you may need to explain your Persona a little bit more then the Celtic guy would, but depending on how historically accurate you want to be it is no more difficult. If you want to be a generic Japanese guy, be prepared to have some odd looks, but it isn't terribly different.
As for the wrongness of it, simply remind anyone who says this about what Corpora says. 'Western Europe or civilizations they had contact with before 1600 ". The Portugese made contact with Japan in the 1400s; in 1592 Hideyoshi (mentioned above) and his son played with an Elephant given to them by the Spanish in order to smooth over some strained relations, especially after the Expulsion Edicts when they were all kicked out and several nuns and priests were (ironically) crucified. So it is no more wrong then any other non Western European country playing in the SCA.
Why Everyone is a Sengoku Jidai Junkie
Okay, a lot of people wonder why most of the Japanese persona you see come from 1467 until 1600, and you very rarely see any from 1000 or 1100. As Furukusu Masahide-tono of the Outlands put it, because "The Buke were Buke, and the Kuge were scared." Simply put, the Sengoku Jidai is the period of the Warrior, the Birth of the Samurai, and the best period to be from if you Fight. Soldiers were second class citizens compared to the Court Aristocracy (Kuge) before 1185; they were absolutly IN CHARGE from the Onin War until the Meiji Restoration in the 19th Century. So playing in the Sengoku, as a Fighter (Heavy or Light), is playing in a time when you were absolute master of your domain, and every Samurai with charisma and a brain for tactics had the possibility of becoming the Shogun.
Some Problems with a Japanese Persona
Every Persona that you could play has some problems. English names are boring, Welsh names are hard to pronounce, and some greek names can lend themselves to modern snackfoods (ho toxhotes becomes ho Dorritos). Being Japanese is no different, and here are some of the things that you can expect.
Heralds Have Problems
I have seen a Herald who can correctly pronounce a fifty one letter Welsh/Celtic name without blinking stumble and stutter over a relatively simple Japanese names because they think it should be more difficult then it is. The thing to remind them, or to know if you are a Herald, is that Japanese names are all pronounced phonetically, because unlike Welsh (which uses the same alphabet differently) Japanese uses a completly different character set; so when it is written in English letters, it is all pronounced phoenetically. But, be prepared to have your name spelled correctly on your scroll, but pronounced incomprehensibly by the Herald who reads the scroll.
These are the people who say the SCA is only Western Europe. Point out the Corpora information from above, and if they don't relent, poke them with a chopstick.
Heraldry Has Problems
Japan didn't have as much of a formalized Heraldry system as Europe did; there was no Chrysanthemum Emperor of Arms, as far as I know. Many clans used the exact same mon (Oda, Saito, etc..) and some of the Mons (heraldry) were incredibly simple. If you have ever played the Legend of Zelda, the Hojo Clan uses the Tri-Force as their heraldry.
In order to be period, Japanese heraldry needs to be very very simple. No more then one charge/charge-group, and only two colors (the backgroumd, and the foreground). But in order to pass through the College of Arms of the SCA, you need to make something that has enough difference from other heraldry to pass. So you'll have to be prepared to compromise.
Merchants Won't Sell (What You Need)
Go to Estrella war and you'll see ten different shops selling shirts, pants, t-tunics, cotehardies, hoopalongs, and leather belts with rings. But you'll be hard pressed to find a place selling a wide variety of kosode, and hakama, obi and geta. Maybe there will be one shop that sells some stuff, if that Japanese Costume Laurel comes out to merchant (I love it when that happens). So, learn to sew or find some friends that know how to sew you can bribe, because otherwise your going tgo spend more then you want to online.
But, all of these problems are overcomable. Being a Japanese persona is great if you love the culture and the history, and can be a lot of fun.