Jurai is a planet within the Milky Way Galaxy, as well as the capital of the largest empire there.
Tenchi Muyo! Ryo-Ohki and Tenchi Muyo! GXP
In the official continuity, the goddess Tsunami and her sisters Washu and Tokimi, the Chousin, searched for eons for a being superior to them. Tsunami descended to the third dimension to search for this kami (God).
150,000-years ago, the giant, sleeping humanoid form of Tsunami was found on the planet of Jurai by a man who would eventually become its first emperor. After waking up, Tsunami detected evidence of potential in this man. Tsunami theorized that his descendants would produce the kami the Chousin were looking for. Thus Tsunami made a pledge to the man of House Masaki to protect him and his descendants and bless them with great power -- her descendants, the Royal Trees. The mighty power of Jurai made way for the planet and its rulers to become a galactic superpower.
Jurai (樹雷星, Juraisei) is ruled by a royal family, the Imperial House of Jurai (樹雷皇家, Juraiouke), all of whom take "Jurai" as part of their names after bonding with one of the Royal Trees, seeds of Tsunami's power which grow into sentient trees and bond to ships of the Juraian Fleet. Before founding and settling on Jurai the families were wandering space pirates and some of their traditions are still based on their pirating past. It can be presumed that the four houses of Jurai were likely originally the four most powerful families, or smaller guilds, in the original larger Jurai Pirate Guild. This resembles the construction of the new Pirate Nation formed in Paradise War, a strategy to unite the presently fractured pirate guilds that was devised by Jurai.
The First Emperor of Jurai, the discoverer of Tsunami, was from House Masaki but the house tends to be made of restless members who would rather roam on adventures than rule, in fact, although the first and most recent emperors come from the house, historically, their family has had the least amount of emperors of Jurai. Many members of the house have abdicated their royal titles or abandoned the planet completely.
House Kamaki used to be a more inconspicuous family until Seto was adopted and from force of her will gave them the impression of being the most politically powerful house on Jurai.
House Amaki tends to be overly ambitious and tends to act in its own self-interest, but the majority of past emperors have been from House Amaki, and they are very proud of the fact.
House Tatsuki tends to be the least forceful of the houses and features the second least emperors of Jurai. However, they tend to be the most approachable house and the most likely to marry into a foreign power's family, forming many political connections throughout the galaxy. House Tasuki also tends to have larger families and the majority of Juraian royalty is comprised of House Tatsuki (not counting all of the Masaki living on Earth).
If the four houses represented the most powerful pirate factions in the former Jurai Pirate Guild, then the citizens would be made of the smaller pirate factions that also formed the guild. One of these factions was most likely the Balta Guild, which split from Jurai to create their own kingdom. It can also be noted that a separate group remained, or reformed, a pirate guild that is not recognized as part of the Jurai Empire, they call themselves the Jurai Star Pirate Guild.
The current Emperor of Jurai is Azusa Masaki Jurai. Azusa Jurai's two wives are the 1st Empress, Funaho Jurai, an earthling (but also direct descendant of Masaki Jurai, who settled on Earth in the far past) and 2nd Empress Misaki Jurai of the House Kamiki, who is also the mother of Princess Ayeka Masaki Jurai and Princess Sasami. The first heir to the throne of Jurai is the son of Emperor Azusa and First Empress Funaho, Prince Yosho Masaki Jurai (a.k.a. Katsuhito Masaki).
Other notable members of the Jurai family are Second Empress Misaki's parents -- Utsutsumi Kamiki Jurai, head of House Kamiki and his wife, Seto Kamiki Jurai, the infamous "Devil Princess of Jurai," an influential figure in galactic politics as well as matchmaker.
Seto is also the reason House Masaki are current rulers as she convinced Azusa, as a child, to return to Jurai. His mother, like so many members of the house, abdicated her royal position to marry a Galaxy Police Officer and had left the house without a head. House Amaki is currently a bitter rival of House Masaki. The intentions of House Tatsuki are still unknown.
The planet Jurai is home to a species of intelligent trees, Royal Trees of the Imperial House (皇家の樹, Oukenoki), descended from the goddess Tsunami. In fact, the name "Jurai" is a combination of the kanji 樹 tree and 雷 thunder. These trees are capable of bestowing great powers and long life to those Juraian royals who are partnered with them and are activated by special devices known as keys. These trees are also used to provide power to Juraian spaceships. All power supplied to the tree ships comes from Tsunami-no-ki, Tsunami's tree form. from a subspace network.
Inheritance to the throne is determined by the connection to a Royal Tree; the higher the Tree is in status, the higher someone in the line of succession. This is why Yosho is first-in-line, due to his connection to 1st-Generation Tree, Funaho. Tenchi's powers as a bearer of the Light Hawk Wings, which are usually generated by Royal Treeships, allow him to be second, as well as his status as Yosho's successor. This is why Seina Yamada is 3rd-in-line, as he found and bonded to a seed of a 1st Generation Tree seed via Idol. Assumingly, Sasami could surpass them all because she's connected to the original Tsunami-no-Ki, but she has not claimed inheritance on these grounds as of yet.
Body Enhancement and Guardians
Other than strength and life derived from partnered trees, Juraians are also masters of body enhancement and Guardian engineering techniques that are unsurpassed in the known galaxy. Bio-enhancement is exactly what it sounds like, a biological enhancement of one's body. A Guardian is an outside augmentation, an energy shield that can be called up or constructs like Ayeka's Azaka and Kamidake that can be called on for extra offense or defense. When Yosho was young, he gifted Airi a Guardian in the form of a ring that she didn't even realize was protecting her until she was attacked. Even regular citizens are feared for their superhuman strength, ability to summon force fields and discharge energy blasts, as demonstrated in True Tenchi Muyo! Volume 1: Jurai, where a trained Galaxy Police officer was not considered a threat to even regular civilians, and in Volume 3: Washu, where a pirate spy, who had undergone decades of enhancement in the Shank Guild to be an ultimate fighter, still couldn't come close to the enhancement of a Juraian prince.
Juraians are also known for their extremely long life spans. Juraians are granted their extended life spans both by their connections to the Royal Trees and their bio-enhancements. In a Q&A session, series creator Masaki Kajishima confirmed that "normal" Juraians have the same lifespan as normal humans (presumably this means without bio-enhancement). Nobuyuki Masaki and others who have Juraian blood but are not bonded to a Royal Tree have expanded life spans thanks to the genetics of being the descendant of Yosho, who has both a connection to a first generation tree and extensive bio-enhancement. Yosho could also extend the life of his family through a connection to Funaho-no-Ki, but his first wife, Kasumi (who did have her life extended this way--until she decided to stop), convinced him not to do this with their children. As a reference, it was mentioned in GXP that the average body enhancement procedure (using Galaxy Federation techniques) increases the average Earthling's lifespan to be around 2,000 years. That is pertaining to the "initial" body enhancement procedure. There are many different types of body enhancements, some for battle, some for mental acuity or other specializations, but Juraian techniques are known to surpass anyone else's.
Prince Yosho and his grandson Tenchi, are first in line for the Juraian throne though Yosho fled his throne for a life on Earth. Ayeka is still Princess but she is second in line as she and Sasami come from a distant branch of the Imperial Family and can only assume the throne if Tenchi refuses and/or she finds a husband. The members of the Imperial Family wield the mighty power of Jurai through unknown means. The members of the royal family retain their ownership of powerful tree ships such as Ayeka's Ryu-Oh whose sap has the power to heal, though it is unknown if they have as many secrets to their power as in the official continuity. In this continuity, Kagato is also apart of the Juraian Royal Family but was banished to the darkest corner of the universe for being too power-hungry after being defeated by Yosho. He returned and took on the missing Yosho's guise to take hold of the throne. At the end of the series, after the defeat of Kagato, Ayeka and Sasami return to their place in the Imperial Family but leave their home to return to Tenchi on Earth. It is unknown who rules Jurai in their stead.
Tenchi in Tokyo
Besides Ayeka and Sasami being the princesses of the planet, there is not much known or said about Jurai except for flashbacks of the main antagonist, Yugi. Yugi was a Juraian child with extraordinary powers and the ability to create demons and have her will done. As an underdeveloped child, she caused chaos on the planet and the then empress Hinase was forced to seal her away on Earth, knowing completely well that she was terrified of the dark. Yugi was released sometime before the beginning of the series, and is now twisted and wants to create her own world on Earth and attempts to distract Tenchi (who has no relation to Jurai in this continuity), the latest Planet Guardian, in order to do this.
Ai Tenchi Muyo
Jurai in Ai Tenchi Muyo seems to be functionally identical to that of Tenchi Universe. A picture of the Juraian globe is shown during a flashback and it looks nearly identical to the one seen in Tenchi Forever, with the two crossing rings. Before getting caught in a dimensional rift and being sent to the present day, the main character introduced in the series, Momo Kawanagare, is depicted as a Juraian princess from hundreds of years in Tenchi's past who is sent to settle on Earth for unknown reasons. Her royal parents are absent from her life and leave her in the care of a bodyguard from infanthood.
In both Pretty Sammy spinoffs of Tenchi Muyo, the name Jurai is instead used for the magical realm called Juraihelm, although the two are vastly different.
- In the 13th episode of GXP, GP Chairwoman, Airi Masaki is seen 'organizing' Lady Seto's memoirs, the script the memoirs are written in resemble Norse/Germanic Runes: Meaning that Jurai's writing system is Rune-based.
- However, in the 7th episode of the OVA, this script also appears when Mihoshi is giving Yukinojo (her ship's AI) her password, which could mean that it is a GP language, OR that it serves as an intergalactic Lingua Franca. It should be noted that it has been revealed in the GXP Novels that it is standard practice in the Galactic Federation civilizations to install some sort of nanomachines into a person's brain (implied to be done at a very young age) that allows that person to immediately understand the intergalactic language and numeric systems. This was also done to Yamada Seina when he first got picked up from home by GP for recruitment.
- The Pirate Nation, founded in Paradise War, bears an interesting similarity to the founding of the Jurai Empire (the plan was spurred in Jurai). The new federation is made of former pirate guilds, led by members of the 4 largest (Daluma, Balta, Shank & Jurai pirates separate from the empire). Jurai was made of former pirates and is now led by four houses. Presumably, the four houses of Jurai were also originally four pirate guilds that united and formed their new nation on a new planet.
- Since Seina Yamada's bond with Jinbu/Zinv was revealed and becoming a part of the Juraian royal family, founding House Yamada, the Kanji characters in Seina's surname, 山田 ("Yama" & "Da") have been combined to become House Yamada's emblem.