Kai Oku serves as a strategist and commander within the Qin military, operating as a trusted vassal to Shou Hei Kun. He lectures at Qin's Strategist Academy, having taught prominent figures like Ka Ryo Ten and Mou Ki. Physically, he sports long black hair typically divided into two ponytails and a long goatee. He consistently wears elaborate robes, whether in combat or during peacetime engagements. His personality blends dutiful loyalty to Shou Hei Kun with a robust demeanor, often teasing others as seen in interactions with Mou Ki and Ka Ryo Ten. He first appears during the Coalition Invasion Arc, monitoring war developments at the palace with other officials. Receiving orders from Shou Hei Kun, he investigates attacks at Bu Pass and later leads nearly 100 elite strategists to reinforce Sai. There, he commands the north wall, identifying vulnerabilities and deploying reinforcements efficiently. During this battle, he encounters his former student Ka Ryo Ten, engaging in lighthearted banter despite the circumstances. In the State of Ai Arc, he is dispatched to Sanyou City to suppress military unrest and uncover plots involving the Queen Mother and Rou Ai, later returning to Kanyou to assist in quelling the uprising. His strategic role expands during the Western Zhao Invasion Arc, where he serves as one of four key planners at the high command headquarters for the Gyou campaign. He also leads a fake supply force and briefly clashes with enemy commander Shun Sui Ju. His abilities span tactical and diplomatic domains. Recognized as a master strategist, he contributes significantly to major campaigns like Sai and Gyou. In combat, he demonstrates proficiency with a podao, holding his own against skilled opponents. His leadership extends to frontline command, and he is later chosen for diplomatic missions, such as negotiating with King Ou An of Han to secure Kan Pishi for Qin. Personality assessments categorize him as an ISTP type, reflecting his practical, analytical approach and situational awareness. His Enneagram type is identified as 6w7, highlighting his need for security, loyalty to superiors and colleagues, and tendency toward cautiousness and worst-case scenario planning. This manifests in his preference for structure and adherence to established procedures, while remaining reliable in crises.