Sae Uryuu serves as a sergeant in the Japan Ground Self-Defense Force and provides tactical support to the Kamui Family against the Zeno Palace empire. As the elder sister of Kanna Uryuu, she joined the military partly to escape the Kamui Family's chaotic disruptions. Her strategic expertise aboard the Shinonome spacecraft elevates the crew's survival odds, offsetting the family's reliance on luck.

Initially portrayed as disciplined, Sae frequently reveals a willful, dogmatic side through her irritation at unsolicited communications like "random faxes" or the Kamui Family's perceived incompetence. She pilots military aircraft skillfully, evidenced when she downed a Luco Zenoid using a Bell AH-1 Cobra.

During the Zeno Palace invasion, Sae's military acumen becomes critical. Tasked with observing the Kamui Family due to their extraterrestrial inheritance and her familial ties, she defies orders when superiors unfairly blame her after failed negotiations. This defiance shifts her role from by-the-book officer to principled combatant. Her tactics remain indispensable to Shinonome's operations, though the Kamui Family continually tests her patience.

Sae shares a close bond with her sister Kanna and their mild-tempered mother, Yoshiko Uryuu. Throughout the conflict, her pragmatic nature and tactical consistency position her as a stabilizing force amid ongoing battles.