This Synopsis was written by me.
Tenchi Masaki is a hapless school boy who suddenly finds himself in the midst of a bunch of women from outer space - among them, space pirate Ryoko, princess Ayeka and her little sister Sasami, scientific genius Washu, ditzy space cop Mihoshi, and the adorable little "cabbit"(part cat, part rabbit), Ryo-ohki. This sets the scene for a hilarious romantic farce as the girls fight for Tenchi's affection, while he fights off various galactic threats and discovers that his family is also connected to the outer space world.
The first series of Tenchi Muyo! is an OVA only, and probably the best and most brilliantly done of all the series'. The second series, Tenchi Universe, starts the saga anew. Tenchi meets the girls in different ways, but the basic plot remains the same. Tenchi Universe also introduces Kiyone, Mihoshi's unfortunate partner police officer. Later episodes involve the villain Kagato wanting to take over the Jurai throne. Tenchi and the gang must go on a major space adventure in order to get to Jurai and stop him. In the third series, Tenchi in Tokyo, Tenchi leaves home to go to school in Tokyo. Of course the girls back home, especially Ryoko and Ayeka, aren't too pleased with this new development. In later episodes, Tenchi falls in love with his schoolmate, Sakuya, which causes broken bonds and separations with the space girls. And things really get intense when Sasami's friend Yugi, who's actually a mutant being, wants to make the world her own "castle." And Tenchi later discovers that Sakuya isn't all that she appears to be, either.