Lt. Makoto Yamamoto serves as first officer aboard the United Planets Space Force destroyer *Soyokaze*. He adheres strictly to military protocols and professionalism, clashing constantly with Captain Tylor's lax command style and disregard for regulations. This ongoing conflict generates significant stress for Yamamoto, leading him to manage his frustration through tranquilizers and medical neuro-cleansing sessions.

Despite his rigid exterior, Yamamoto exhibits emotional vulnerability, easily moved by dramatic speeches and prone to publicly exhibiting sentimentality or fear. He harbors strong ambition to command his own vessel, eagerly seizing any opportunity to assume temporary captain duties. Throughout the series, Yamamoto remains conflicted between his duty to report Tylor's perceived incompetence to superiors and his ingrained loyalty to the chain of command.

Yamamoto undergoes notable development, gradually softening toward Tylor's methods. By the series' conclusion, he adopts some of Tylor's unconventional approaches while retaining his core professionalism. He ultimately acknowledges Tylor as the *Soyokaze*'s only suitable captain, fully supporting his command despite earlier reservations.

In later media, specifically the manga *Love & War*, Commander Yamamoto serves as staff officer and adjutant to Vice Admiral Tylor aboard the battleship *Omi*. He embarks on a time-travel mission to the Raalgon Empire's past alongside Tylor and his fiancée, Lt. Commander Yuriko Star.