1.)In the original Gundam SEED series, Cagalli is first seen disguised as a civilian in Morgenrote, the military factory where the Earth Alliance's secret mobile suits were being developed. The colony was subsequently attacked by

2.) ZAFT forces, who were quite eager to secure the new weapons. Upon discovering the units, she cried that her father was a traitor, presumably for letting Orb develop weapons for the Earth Forces. This was when she met Kira Yamato for the first time since they were separated at birth. Just prior to the destruction of the colony, Kira pushed her into a lifepod.

3.) Cagalli reappeared later in the Bloody Valentine War as a member of the Desert Dawn Resistance Movement in ZAFT-occupied northern Africa. Here she revealed her true identity for the first time as Cagalli Yula Athha, the daughter of the Orb Union president. So in actuality, Cagalli was the Princess of a neutral Earth Nation, although she had decided to fight with the Resistance Movement in Africa on her own terms. During this time she also encountered Kira Yamato again as he spent time on Earth with the Archangel ship. Initially they seemed to clash with one another. However, Cagalli and Kira soon become quite close as they shared a friendly affection for each other.

4.) Sometime later, Cagalli's FX-550 Skygrasper craft was shot down after aiding the Archangel as a pilot in a brief battle against ZAFT forces. In a twist of fate, she was marooned on an island with ZAFT mobile suit pilot Athrun Zala. Initially enemies, they soon called a truce in order to co-exist with one another. However, their different view points pertaining to the war clashed and it didn't seem that they would ever agree. Yet, by sharing their varying opinions, both Athrun and Cagalli began to experience an inner revelation- Was this war really necessary? It was evident how quickly one tragic battle was used as justification for more killing. It was another sad reminder of the needlessness of war for both parties. Not long afterwards, both Athrun and Cagalli were rescued off the island. But, when they parted it was more with fondness than anything else. Little did they know that they shared a mutual friendship with Kira Yamato and would be seeing each other again on several occasions. It's during these encounters that an affection seemed to be growing between the two. Later in Orb, Cagalli tries to help Kira's internal suffering by reuniting him with his family, but he refuses to see them at that moment, telling her to apologize to them for him. Cagalli's worry over Kira's health and state of mind culminate in her embracing him tightly before he left Orb with the Archangel, telling him not to die and to come back to see her again.

5.) After an intense battle where Kira and Athrun almost kill each other, Cagalli finds the latter lying unconscious on a beach. When Athrun regains consciousness, she points a gun at him and asks what happened to Kira. Basically, Athrun says he took Kira's life and cries because they used to be the best of friends. Cagalli cries as well and asks Athrun why he would do such a thing if they were such good friends, and Athrun retorts the reason he did it was because Kira killed his friend Nicol Amarfi. Cagalli calls him an idiot and asks what is the point in killing someone because someone else was killed, how is that twisted logic ever going to bring peace. Upon hearing these questions, Athrun just grimaces and weeps bitterly.

6.) Before releasing him back to ZAFT, Cagalli gives Athrun the haumea and says she doesn't want anybody else she cares about to die.

7.) Later when Kira returns to Orb aboard the Archangel after acquiring the ZGMF-X10A Freedom, a tearful Cagalli embraces him and knocks him to the floor. She then beats him up and calls him an idiot and sorrowfully tells him that she feared she'd never see him again. Kira assures her that he is indeed alive and that he kept his promise to come back which shocks yet comforts her almost immediately. Kira then explains what happened between him and Athrun. Firstly, he killed Nicol, but in the next battle Athrun killed his friend, Tolle Koenig, while he was piloting the FX-550 Skygrasper, the same one formerly piloted by Cagalli no less, which makes her shudder.

8.) Cagalli eventually joined the crew of the Archangel when the ship arrived to Orb shortly before the Earth Alliance invaded her country. During the invasion, Athrun joined the fight in the ZGMF-X09A Justice Gundam, the Freedom's brother unit. He was originally sent to retake or destroy the Freedom, but instead he helps Kira and the others stave off the Earth Alliance. After doing so, a tearful Cagalli runs up to Kira and Athrun as they meet face-to-face and hugs them both.

9.) Although they finally manage to patch things up, this happy reunion is quickly ruined when the Earth Alliance attacks again and Uzumi Nara Athha sacrifices his life in order to prevent them from getting their hands on the mass driver. Before that happens, however, he gives Cagalli a photograph of her and Kira when they were babies and tells her that although she is leaving her father she won't be alone, for she will be with her brother.

10.) In the final phases of the Bloody Valentine War she piloted the MBF-02 Strike Rouge as member of the Three Ships Alliance. Although she is a Natural, in battle she is also capable of going into SEED Mode, like Kira and Athrun. In SEED mode, she is comparable in combat skill to her brother (as he normally fights).

11.) During their time together as part of the Three Ships Alliance, Athrun and Cagalli begin to develop romantic feelings for one another. In fact, during the final battle Cagalli saved Athrun's life in the destruction of GENESIS by reminding him that he has the courage to keep on living. Together, they find Kira floating in space not far from a heavily-damaged Freedom, after they both shed tears of joy, they proceed to rescue Kira and recover the Freedom so that it can be rebuilt.