Achika and Nobuyuki
Tenchi's parents. Achika isn't in the series, and has only had one major appearence, in the movie 'Tenchi Muyo In Love.' The reason this is, is because she died when Tenchi was really young. In the series they didn't give you much info on her death, but in TMiL they give you a better idea as to what the cause was. Achika is the daughter of Yosho, Prince of Jurai. In TMiL, Achika battles Kain, and this drains a great deal of her life force.
After Achika's death, Nobuyuki was never really the same. He became quite the little perv.
Ayeka
She is a member of royal family of the planet Jurai. Actually she's the crown princess. She is on a long search for her half brother Yosho,Tenchi's Grandfather, the Crown Prince of Jurai. At one time Ayeka and Yosho had plans to marry. (Jurai custom is a little different than ours, it is rather common for relatives to marry. Neither of them were objecting to the marrige.)
Sometimes Ayeka seems to be very up-tight and always tries to do “what a princess would”.
While tracking Yosho's flight path from his pursuit she happens upon Earth. She locates Ryoko who was the fugitive that Yosho was pursuing before he disappeared. Ryoko is a wanted space pirate. Ayeka hates Ryoko and tries to catch Ryoko. Ryoko's ship Ryo-ohki gets into a battle with Ayeka's ship, named Ryou-uh ,and is damaged so bad that she along with her younger sister Sasami are forced to stay on Earth with Tenchi for a while.
Ayeka appears to have a calm, sensible personality but what lies underneath is totally different. She has a temper like a firecracker and once she wants something nothing will usually be able to stop her. She is also in love with Tenchi and is constantly fighting with Ryoko for him
Kiyone
She is the biggest victim in the whole Tenchi television series. No one has ever had more bad luck then this unlucky detective.
She passed the Galaxy Police exams with scores unheard of, and was even named the best rookie cop. Her career seemed endless until Mihoshi was assigned as her partner.
After Mihoshi became Kiyone's partner everything started going down from there. They are now stationed on the far away backwater planet of Earth as planetary contacts.
Kiyone is a very calm, sensible person who is always in control of the situation. This can be a weakness which has been exploited by Mihoshi alot to get Kiyone to do whatever she wants.
Mihoshi
She gives new meaning to the term "dumb blonde". She is Kiyone's partner in the Galaxy Police, much to Kiyone's displeasure.
She is always hungry and is always clueless to whats happening around her. It took her six episodes to figure out that Ryo-oh-ki was a girl.
Ryoko
An extremely powerful space pirate who has the ability to fly, phase through matter, teleport to places she's been to, and create a sword made out of energy or just throw energy balls.
She is quick to anger, selfish and violent at first but after living in the Masaki household you can see her change into a better person. She is in love with Tenchi as is her rival Ayeka and they are both trying constantly to gain his attention and approval.
Sasami
Ayeka's little sister and second princess of Jurai, is amazingly one of the more mature characters in the Tenchi television series.
Although she still has childish tendencies like being naive and always curious, Sasami is the most understanding and hardest working in the whole group. She cooks the dinners and does most of the housework
Tenchi Masaki
A normal seventeen year old teenager who's mother passed away when he was a little boy. He lives with his father in a house near the Masaki shrine. From childhood he has been training with his grandfather in the art of swordfighting.
The adventure of his life starts one day as he walks home from school and happens to notice a streak across the sky. Later he hears an explosion and heads off to see what it was. When he arrives he finds Ryoko passed out. He revives her and protects her from Mihoshi in mecha armor. After that the adventure begins as other things happen.
Tenchi is a very kind-hearted person, he rarely ever gets mad and is nice about everything.
Tsunami
Is the power of the Jurai. Tsunami was the first tree and source of all trees of power,each generation below Tsunami contains less power than the previous. Her human form looks like an older version of Sasami and is in fact closely linked to Sasami.
She is one the the three goddesses as well.
Washu
Professor Washu was exiled for 700 years because she created destructive things such as galaxy destroying guns and dimensional oscillating bullets, was released in the Masaki shrine when Ryoko and Ayeka were fighting in it. Ryoko hit the crystal hard enough for it to crack and release Washu.
While she looks like a child she is 20,000 years old or even older! She can create almost anything in her subspace lab built in the Masaki house.
Using her great scientific genius she has been able hook certain places in the Masaki household to different dimensions. Her lab is through the broom closet and she even made a girls bathroom which only the girls can get into.
Washu is one of the more crazy characters in the show. She is playful and very confident in herself. She is also one of the three Goddesses however her memory has been erased of this.
Yosho
Ayeka's half brother, Achika's father, and Tenchi's Grandfather. He came to Earth in pursuit of the Demon Ryoko, and he imprisoned her inside a cave. Taking her gems and embedding them into his sword, he sealed the cave, Ryoko never to be released. Well, not really, seeing as how Tenchi let her out. Yosho was calling himself Katsuhito on Earth, and he took the appearance of an older man, so that he might fit in.
Jurai custom permits siblings to marry, it is a quite common act on their planet. Yosho was to marry Princess Ayeka. Ayeka came to Earth in search of her beloved, but couldn't find him... untill Kagato shows up, and everything is blown into the open. When Ayeka discovers Yosho has grown into a withered old man, she grows sad. Yosho suggests that it be better they weren't together, and this little discussion pretty much comes to a halt when he jokingly says something like 'Ok Ayeka, lets go get married now.' This all ends in Yosho basically giving Ayeka to Tenchi, or Tenchi to Ayeka...?
Yosho is also the keeper of the Masaki family shrine. Yosho has aged ( On Jurai he would not have ) because on Earth there is no “Water of Life” (something that Juraians rely on for their long life).