Yoshikazu Aihara is the Chief Communications Officer of the space battleship Yamato during its 2199 AD mission to Iscandar. Possessing special clearance for the deep space communications room, he exhibits exceptional skill operating the ship's radio equipment. His responsibilities include managing vital communications between the Yamato and Earth, and facilitating contact with Iscandar.

During the voyage, Aihara secretly maintains regular contact with his family via a Garmillas relay satellite monitoring transmissions. Learning of his father's critical illness triggers intense homesickness and panic. In an emotional crisis, he implores Navigation Officer Daisuke Shima to return the ship to Earth, voicing doubts about the mission. Overwhelmed, he attempts to abandon ship by floating towards Earth in a spacesuit. This desperate act leads him to discover the hidden Garmillas relay satellite, resulting in his rescue by the Cosmo Tigers. The experience restores his composure, allowing him to resume duties.

Aihara later demonstrates particular proficiency handling communications involving Trelaina of Telezart during the Yamato's 2202 AD mission. Daisuke Shima frequently expresses enthusiasm for direct communication with Trelaina, sometimes requesting Aihara operate the equipment while he speaks.

In subsequent assignments, such as during the "Ark of the Stars" events, Aihara continues serving as communication chief. Junior officers, including backup bridge radio operator Jun Ichikawa, work under him.

After leaving the Yamato, Aihara transfers to the battleship Hyuga, assuming the position of head of the operations division.

A naming inconsistency exists across missions: he identifies as "Yoshikazu" in the first season but uses "Giichi" in the third season due to a continuity error. His favorite song is "Kitakami Yakyoku" (北上夜曲).