Lady Une is known as Treize's right-hand woman and has a reputation for being a fierce commander. She was responsible for assassinating Vice Foreign Minister Darlian due to his knowledge about OZ, and also ordered the murder of Relena when she witnessed the crime. Her methods were brutal and ruthless but effective. During a battle with the Gundams, she forced their surrender by threatening to destroy a colony using Alliance missile satellites. Afterward, Treize encouraged her to be more graceful, which led to a personality conflict and resulted in her developing a new persona with a gentle, beatific attitude.
As Treize began to split with Romefeller, Lady Une was sent to free Duo, Wufei and the Gundam engineers from the Lunar Base but was shot by Chief Tsubarov. While recovering from her wound, Une had time to resolve her personal conflict. Shortly after the end of the war, Une was picked to become the leader of the new Earth governments peace watch group, Preventer.
Her timely intervention saved the lives of both Relena and Mariemaia, revealing that Dekims actions were not in line with Treizes philosophy. Once the rebellion ended, Lady Une decided to take care of Mariemaia, but kept her position as Preventers head.