Yoshikazu Aihara is a 22-year-old ensign in the United Nations Cosmo Navy, serving as a communications officer on the bridge of the space battleship Yamato. His critical role involves managing communications and sensor systems during the vessel's interstellar voyages, detecting and interpreting signals across vast distances.

During an emergency warp, the Yamato encountered a mysterious planet. While the survey team investigated an alien structure, Aihara detected an SOS signal. He traced this signal to its unexpected source: the wreck of the historically sunken World War II-era battleship Yamato, resting within the planet's anomalous jungle.

Entering the wreck led to a communication blackout, severing contact with their shuttle. Aihara became trapped inside the structure with other crew members and encountered Garmillas personnel. The environment altered their appearances, causing weapons and uniforms to vanish, replaced by civilian attire. Over several days of confinement, Aihara participated in cooperative efforts with both human and Garmillas personnel to escape their shared predicament.

Following his assignments on the Yamato during its initial and subsequent missions, Aihara's career progressed to head of the operations division aboard the Hyuga.