Aihara serves as the chief communications officer on the bridge of the space battleship Yamato, holding the rank of ensign in the United Nations Cosmo Navy. His background is rooted on a struggling Earth; his family originally comes from Iwate Prefecture in northern Japan, and like many others during the war, they live in an underground city to survive the planetary crisis. Before his naval service, Aihara was a student whose life was disrupted by the wartime circumstances, leading to his recruitment as a communications specialist for the critical mission to Iscandar.

Aihara's personality is defined by a deep emotional sensitivity and a strong attachment to his home and family. This vulnerability becomes the central focus of his character during the Yamato's maiden voyage. As the ship travels farther from Earth, he suffers from intense homesickness and stress, a condition noticed by the ship's doctor. His core motivation is rooted in love and concern for his parents, particularly his father. When a Gamilas relay satellite secretly allows the Yamato to communicate with Earth, Aihara discovers that the situation at home has worsened, with food riots and his father fatally injured. This news triggers a profound psychological crisis. In his despair, he questions the validity of the mission, begging the navigator to turn the ship back, and ultimately dons a spacesuit to leap into the void of space, hallucinating that he can float back to Earth. It is only upon discovering the alien relay satellite that he realizes he has been manipulated, and he regains his senses, allowing himself to be rescued. This episode marks a significant development for Aihara, moving him from a background role to a crew member with a recognizable inner life and a story about overcoming psychological manipulation and reaffirming his duty.

In his role on the bridge, Aihara is responsible for managing all of the Yamato's communications, including detecting and interpreting signals across vast interstellar distances. He is portrayed as highly skilled at operating the ship's radio equipment. His position grants him special clearance to the deep-space communications room, a privilege that initially allows his unauthorized contact with Earth. He maintains close working relationships with other bridge officers, including the second-in-command Yasuo Nanbu and the helmsman Kenjiro Ohta. On a later mission, Aihara becomes involved in a long-distance romance with Akiko Todo, the granddaughter of a high-ranking Earth Defense Force official, a relationship that develops through his communications duties and provides a lighter subplot.

Beyond his technical proficiency, Aihara's notable abilities lie in his acute sensitivity to signals, which can be both a strength and a liability. He is the first to detect the restored communications with Earth, but this same attunement makes him susceptible to the psychological warfare waged by the Gamilas. After his crisis and recovery, he continues to serve on the Yamato through multiple subsequent missions, including conflicts with the Comet Empire and the Bolar Federation. His career progresses beyond the Yamato as well; after his tenure on the famous battleship, he transfers to the battleship Hyuga, where he is promoted to head of the operations division. An inconsistency exists regarding his given name: it is written with the same kanji characters, but is pronounced as Yoshikazu in the first series and as Giichi in the third series.