Captain Kouji Wada was an officer in the Seventh Division of the Imperial Japanese Army. He is visually distinguished by a prominent mustache that extends from beneath his nose to the sides of his chin, along with slanted eyes and eyebrows. He served within the military hierarchy under Lieutenant Colonel Tokushirou Tsurumi.

Wada's personality is marked by a degree of pride and a willingness to openly criticize his superior. His motivations appear to center on adherence to a sense of propriety and order within the military chain of command, which ultimately leads him to challenge Tsurumi's authority. This defiance, however, proves to be a fatal misjudgment.

His role in the story is brief but significant as an illustration of the ruthless environment within the Seventh Division. After berating Tsurumi for his actions or methods, Wada is betrayed and killed by Hajime Tsukishima, a loyal subordinate of Tsurumi. This event underscores Tsurumi's absolute control over his men and the lethal consequences of disloyalty or dissent within his ranks.

Wada's key relationship is with Tsurumi, whom he confronts, and with Tsukishima, who carries out the execution. There is no notable development for the character, as his appearance is limited to this single act of defiance and his subsequent death. His notable ability, if it can be called one, is his willingness to speak against a dangerous superior, a trait that sets him apart from the many soldiers who blindly follow Tsurumi. He is a minor character whose primary function is to demonstrate the high stakes and internal brutality of the Seventh Division's pursuit of the gold.