Ryuko Saito

The antagonist of the story, Saito is a mysterious scientist and time-traveler who attempts to thwart Gawl, Koji, and Ryo. She uses Dr. Tekuma Nekasa's desire to recover his past to bend him to her will. She is constantly calling Generators to do her dirty work and often tries to kill or capture Gawl and his friends.

(Source: Wikipedia)