The Juraian empire came to be as the man who would become the first king of Jurai stumbled upon a sleeping Tsunami-kami-sama. She then guaranteed to protect the Masaki line for generations to come. It should be noted that Tsunami seemed to have been at that spot a long time, no doubt the chousin's ability to see ahead into the future.
The planet Jurai is ruled by a royal family, the , all of whom take "Jurai" as part of their names after bonding with one of the royal trees. The most notable of them is First Princess Ayeka Masaki Jurai, who is in love with the anime's main character Tenchi Masaki. She is the daughter of the Emperor of Jurai, Azusa Masaki Jurai. Azusa Jurai's two wives are Funaho Masaki Jurai, First Queen, and Misaki Kamiki Jurai, Second Queen.
The child of Azusa Jurai and Funaho is Yosho, a.k.a. Katsuhito Masaki, who is Tenchi's grandfather; the children of Azusa Jurai and Misaki are Ayeka and Sasami Masaki Jurai, who came to Earth to look for Yosho when he disappeared. In some versions, the relationship between Yosho and Ayeka is stated to be more distant.
There are four royal houses on Jurai, these being House Masaki, House Kamiki, House Tatsuki and House Amaki. Probably the most famous house is Kamiki, this being that it has the famed 'devil princess of Jurai', Seto Kamiki Jurai. Seto is also the reason House Masaki are current rulers as she stopped the house from becoming extinct when numerous members kept running away or left Jurai. 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 descended from the goddess Tsunami-kami-sama. 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 from a subspace network.
Juraians are also feared throughout the Galaxy for their superhuman strength, as demonstrated in the True Tenchi Novels where a trained Galaxy Police officer was not considered a threat to even regular civilians. Juraians are also known for their extremely long life spans, as Ayeka looks about the same age as Tenchi, but she is much, much older than he is. A comment that Ayeka makes during the OVA's fifth episode may hint towards these huge life spans having something to do with the planet's trees. In a Q&A session, series creator Masaki Kajishima confirmed that "normal" Juraians have the same lifespan as normal humans.
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.