Colonel Kouma is the military chief of the Japanese forces established to counter the threat of Ajin. He holds the rank of Colonel and commands the Anti-Ajin Special Force, an elite unit ostensibly created to deal with demi-human terrorists and incidents. Despite his high position, Kouma finds himself constrained by the political realities and orders passed down from his superiors within the government. This places him in a complicated position where his personal judgment often conflicts with official directives.

In terms of personality, Colonel Kouma is depicted as a disciplined and pragmatic military man. He is not presented as a zealot or an overly emotional figure; rather, he carries out his duties with a sense of stoic responsibility. However, he is not blindly obedient. As the series progresses, it becomes clear that he is acutely aware of the political gamesmanship surrounding him. He confesses to Tosaki that he realized the elite unit was never truly intended for deployment after receiving insignia marked "Anti-Ajin Human Special Forces," a designation that contradicted the unit's supposed secrecy and suggested it was merely for show. Despite this cynical reality, Tosaki notes that Kouma is not the type of person to let such political posturing affect the rigorous training of his men, implying a deep-seated professionalism and dedication to his role.

Kouma's primary motivation appears to be adherence to military protocol and the chain of command, even when he personally disagrees with the outcome. He denies Tosaki's requests to deploy the special forces against the terrorist Satō, citing orders from above, but he does so without malice, simply stating the limitations of his authority. There is a sense that he is a man trapped by a system that does not want to utilize its most effective tool, leaving him to watch from the sidelines as others are sent to face a nearly invincible enemy. His key relationship is with Yu Tosaki, a government agent who is fiercely determined to stop Satō. Their interactions are tense yet respectful, built on a mutual understanding of the difficult nature of their work. Tosaki challenges Kouma’s compliance, asking if he regrets sending people to hell with his inaction, suggesting that Kouma bears a quiet burden of responsibility for the consequences of following orders.

In the story, Colonel Kouma serves as a representation of the official, institutional response to the Ajin crisis, contrasted with the more rogue, unconventional methods of characters like Tosaki and Kei Nagai. His role is primarily that of a gatekeeper; he holds the military might that could potentially turn the tide against Satō but is initially prevented from using it. This creates a significant obstacle for the protagonists as they prepare for their final confrontation. While his character does not undergo a dramatic personal transformation, his development is marked by a subtle shift from passive compliance to eventually authorizing his forces to engage, presumably after the situation escalates beyond the control of civilian authorities following the fall of Iruma Base. Regarding notable abilities, his strengths lie in command, strategy, and the authority he wields over a highly trained military unit rather than any personal combat prowess.