Lacus Clyne is a pop idol among the PLANTs, owing to both the influence of her father Siegel Clyne, Supreme Council chairmen of PLANT, and her beautiful singing voice (which many suspect may have developed due to her being a Coordinator). Near the beginning of the series she was engaged to Athrun Zala through an arranged marriage. Though (according to the drama CD) the two were in love when they first met, their feelings diminished as time went on and the engagement became more political then ever before.
The pink-haired princess enters the series when she is traveling in a civilian vessel for a memorial ceremony on Junius Seven. The ship is mistaken for a ZAFT military aircraft, and is attacked by the Earth Alliance. Lacus is escorted to a lifepod, and escapes safely. Shortly thereafter, Lacus' escape pod is discovered by Kira in the Strike. He brings the pod back to the Archangel.
The doors to the life pod open and out hops a small, pink, robotic ball. Following after it is Lacus Clyne herself in a bit of dismay that she was saved by Earth forces. Despite being enemies, the girl is cheery and kind to everyone on the ship as they keep her hostage. ZAFT forces discover the Archangel, and a battle breaks out. Before the Earth Alliance can suffer more loss, Natarle Badgiruel opens a channel to the enemy. It is then revealed to ZAFT that Lacus Clyne, the famous idol, is onboard the Archangel.
Kira is distraught and, due to Flay's abusive words, comes direly close to an emotional breakdown; however, Lacus attempts to comfort him. The couple find that they both know Athrun Zala on a personal level, and even that Athrun made Lacus' Haro/Pink-chan (her pink, robotic ball) and Kira's Torii (his flying bird robot). Kira decides to return Lacus to where she belongs with Athrun.
Even before meeting Kira, Lacus had an indirect influence on the war. She spread her opinion throughout PLANT by singing a song of peace, her lyrics filled with the hope of harmony between the nations. After encountering the Archangel, she expresses a larger need to achieve peace by aiding Kira many more times, causing Athrun to question his purpose for taking part in the war, and much more.
