Kouga Tatsuma is a 36-year-old police officer in the Public Security Bureau, responsible for monitoring Scards and maintaining order within Akatsuki special ward. He stands 188 cm tall, with dark green hair and brown eyes, and his birthday is November 8. Kouga possesses the Divine Tattoo of Fafnir, enabling him to amplify physical strength, either his own or that of materials he interacts with.

Externally, Kouga projects a good-natured, approachable demeanor. He frequently uses nicknames and speaks softly and gently, fostering a perception of him as a kind, uncle-like figure. This affable exterior masks a contrasting underlying personality characterized by pragmatism and ruthlessness in achieving objectives; he is willing to employ any means necessary, including brutal methods. He often offers advice to colleagues, particularly his partner Itsuki Torataka, in a manner reminiscent of an elder sharing wisdom, though Itsuki rarely takes this guidance seriously. Kouga and Itsuki collaborate within the Public Security Bureau's special Scard unit, wearing identical uniforms.

Kouga's operational philosophy prioritizes results above all, exemplified by his stated willingness to do whatever it takes to protect his family. Personality assessments categorize him as an INTJ with an Enneagram Type 8w9, indicating strategic focus, assertiveness, independence, and a strong protective instinct, especially toward his team. He exhibits a commanding presence and a preference for control, communicating directly and confidently. Loyalty to his comrades is paramount, coupled with a readiness to act decisively for their safety.

Kouga's documented involvement centers solely on his duties as a Scard operative utilizing the Fafnir tattoo's power within the Akatsuki ward, operating amidst its three contending organizations.