Tenchi Masaki used to be an average Japanese 17 year old boy, hard working and
shy around girls. He lived with his father Nobuyuki, and every summer he would
visit his grandfather at the Masaki Shrine to help keep the shrine clean as
well as train in sword fighting (his grandfather is an excellent swordsman).
Tenchi's mother, Achika, died when Tenchi was only six, and thus Tenchi's family
consisted of his grandfather, father, and himself.
Tenchi's life turns upside down, however, when he first releases Ryouko from a cave near his grandfather's shrine. One thing leads to another, and Tenchi soon finds himself surrounded by beautiful young female aliens. He befriends them all, and as time passes he accepts all of them as family, even though all of them are in love with him and constantly compete for his affections.
Even though Tenchi is shy around the girls, he cares for all of them and would do whatever it takes to keep any of them from harm. He is also a very patient young man, which is a very good thing to be considering the constant bickering that goes on between his friends, especially between Aeka and Ryouko.
Later in the series, we find out that Tenchi is in fact descended from the Juraian royal family (this of course makes Aeka very happy). We also find out that Tenchi isn't exactly the normal boy he thought he was. He harbors many powers, like the ability to create Light Hawk Wings, a powerful offensive and defensive weapon thought only could be created by Juraian ships. He also has use of the tenchiken, an energy sword that bears the same name as he does. This sword has the ability to control all Juraian ships.
Of course, the perpetual question everyone asks is,"Who will Tenchi choose for his wife?" While most times it seems like he and Aeka are close, there are other times where he and Ryouko share touching moments. Not to mention that even though Sasami is only eight now, we have seen glimpses of how she will look in the future, and even Aeka and Ryouko admit that she will be more beautiful they they are. Lord Tenchi definitely has his work cut out for him...