Kaori Sagawa pilots the GL-3 mecha for the Planetary Defense Forces Alliance. She operates within a three-pilot squad alongside Hiroshi Akishima (GL-2 pilot) and Ken Tazaki (GL-1 pilot and squad leader), defending Japan against the alien FOS invasion. Her combat role involves aerial engagements utilizing the GL unit's primary 60mm variable assault rifle and optional sub-weapons like missile pods.

Sagawa's duties place her directly in the critical Plan Zed counteroffensive. This operation necessitates deactivating Earth's Diffuser shield for precisely 14 minutes, leaving the planet exposed while a superweapon charges to target the FOS mothership. During this vulnerable window, Sagawa engages in defensive combat operations to protect the weapon's activation site from attacking FOS forces.