Giichi Aihara, also called Yoshikazu Aihara, held the position of Chief Communications Officer on the Yamato. His family originated from Iwate Prefecture in northern Japan, with both parents living in an underground city on Earth during the ship's first voyage to Iscandar.

Approximately two months into that mission, Aihara suffered significant psychological distress due to separation anxiety and worry for his family. Medical staff diagnosed accumulated stress, prescribing a therapeutic session in the holography room. The simulation recreated his snowy hometown, provoking a strong emotional reaction when a holographic representation of his mother appeared.

Later contact with Earth revealed worsening conditions underground. Through unauthorized communication, Aihara learned his father had participated in resource riots sparked by shortages and suffered fatal injuries. His mother confirmed the death during this transmission. This news triggered an emotional crisis, leading Aihara to confront crewmates over perceived mission futility and attempt an unauthorized spacesuit departure before intervention.

Before the Yamato's third mission, at Southern Cross Island (alternately recorded as "Southern Island"), Aihara had a romantic encounter. He met Akiko Todo, granddaughter of EDF Commander Heikuro Todo, bonding while burying a dead bird. They parted without exchanging identities, though Aihara kept a chrysanthemum she gave him. They reunited when she visited the Yamato prior to its next departure; his nervous reintroduction amused observers.

Professionally, his consistent duty involved managing communications, including monitoring transmissions and operating bridge equipment. He fulfilled this role under various commanding officers, including Captain Juzo Okita during the conflict against the Dinguil when their water planet Aquarius threatened Earth. His documented actions during this final mission remained within standard duties.

Aihara served aboard the Yamato during multiple deployments: the original Iscandar mission, the Comet Empire conflict, the journey to Bolar Federation territory, and the Aquarius crisis. Crewmates consistently used his operational callsign, Homer, while his family referred to him as Yoshikazu in communications.