Yamamoto Makoto is the first officer of the United Planets Space Force destroyer Soyokaze, holding the rank of lieutenant. He strictly adheres to military regulations and protocols, emphasizing discipline, order, and professionalism. This dedication frequently clashes with the ship's captain's unconventional command style, causing Yamamoto significant frustration. To manage this stress, he often uses tranquilizers and undergoes neuro-cleansing treatments in the ship's medical office.

Initially viewing the captain as incompetent, Yamamoto wrestles with the conflict between obeying military codes and reporting perceived negligence. He actively seeks his own command position throughout the series, believing he could enforce proper standards more effectively. However, exposure to the captain's unexpected successes and unorthodox methods gradually shifts Yamamoto's perspective. By the main storyline's conclusion, he demonstrates reluctant but tangible respect for the captain's effective leadership, despite its deviation from traditional doctrine.

In later developments, Yamamoto achieves promotion to commanding officer of the new vessel Aso. This partially fulfills his career ambitions. Yet, his crew ultimately departs to serve under the former captain, leaving Yamamoto to assume command of the Aso alone. This outcome highlights the persistence of his professional ideals alongside an acceptance of the Soyokaze crew's unique dynamics.