Zero is Dr. Clay’s favorite invention (notice that the sign that he puts on all of his fav inventions is on her. . .). Her specialties run toward assuming the form of whomever she chooses (or Dr. Clay chooses). Zero serves Dr. Clay hence Lady Tokimi.

Under Dr. Clay’s orders, Zero assumes Ryoko’s form and sends her up to Dr. Clay’s ship. Zero then assumes Ryoko’s life in order to “try” and capture Washu. When Zero copied Ryoko’s body, she subsequently copied her personality and her love for Tenchi. Whenever Zero tried to capture Washu, Tenchi would pop-up, leaving Zero gaga. Finally, Dr. Clay got fed up and ordered Zero to eliminate him b/c he was distracting her from her mission. Well, you know that if Zero copied Ryoko’s personality AND love for Tenchi, she can never hurt Tenchi.

Tenchi and the gang find out that Dr. Clay is holding Ryoko captive and go to rescue her. Dr. Clay damages Zero severely. The only way that Washu could save Zero was to combine Ryoko and Zero. Hey! It sounds worse than it actually is . . . it’s like combining Ryoko with Ryoko. Since Zero copied everything of Ryoko, she was basically like an identical Ryoko with programming.