Yasuo Nanbu serves as a tactical officer within the Yamato fleet, integral to coordinating weapon systems and combat strategies. As second-in-command of the Yamato’s tactical division, he orchestrates the deployment of primary and secondary artillery, torpedo launches, and fighter squadron operations during missions.

In the 2199 timeline, his role evolves: a United Nations Cosmo Navy officer, he initially acts as the Yamato’s chief gunner across its first two voyages, directly commanding cannons, missiles, and the pivotal wave-motion gun. Later, he transfers to the Asuka, a Yamato-class sister ship, ascending to head its tactical division and assume duties as executive officer.

His technical proficiency stems from his lineage—Nanbu Heavy Industry, a leading munitions manufacturer—though his military career strained familial relations. During his Yamato tenure, he holds the rank of Lieutenant Junior Grade (Second-grade Space Lieutenant), blending inherited engineering acumen with tactical leadership.