Kou Yoku, epithet "Thunder," serves as a military commander from the state of Chu. He belongs to Chu's younger generation of officers, contemporaries in age to Qin commanders like Ri Shin, Ou Hon, and Mou Ten. Details of his early life are scarce, though he joined the Chu military in his early teens and rapidly ascended to 100-man commander based on combat talents and swordsmanship. Physically, Kou Yoku is clean-shaven with shoulder-length, greasy-looking black hair. He possesses a muscular build and sports numerous scars across his body, particularly on his arms. His personality is rude, laid-back, yet intensely focused during combat. He exhibits arrogance and a loud demeanor, frequently taunting opponents, though he demonstrates greater pragmatism and intelligence than some rivals tactically. He is an instinctual-type fighter. For years, Kou Yoku served under General Rin Bu Kun alongside his best friend and fellow prodigy Haku Rei, primarily along Chu's southern battle lines. During this service, he developed deep respect for Rin Bu Kun, viewing him as the ideal model of a general, and relied on Haku Rei's archery skills for battlefield support. His combat lethality is enhanced through his mastery of the legendary *Bakuya Sword*, placing him among the series' most powerful swordsmen. Official statistics rate his strength at 91, command at 86, and intelligence at 78. Kou Yoku first appeared during the Sanyou Aftermath Arc, stationed at the Qin-Chu border. He provoked the Hi Shin Unit with three consecutive days of arrow fire, leading to a brief clash with Ri Shin where both traded blows evenly until Haku Rei intervened. In the Coalition Invasion Arc, he joined the Chu invasion of Qin within Rin Bu Kun's 1st Army. He engaged Mou Ten and Ou Hon in combat; his duel against Ou Hon ended upon learning of Rin Bu Kun's death at the hands of Qin General Tou. Rin Bu Kun's death profoundly affected Kou Yoku; he wept openly during the cremation and swore vengeance against Tou. Transferred to General Ka Rin's 2nd Army, he received promotion to 5000-man commander and orders to target Tou. During their confrontation, Kou Yoku wielded the *Bakuya Sword* to fight Tou to a temporary standstill, strategically deploying his troops to occupy the Qin general while Ka Rin's forces advanced. This duel forced Tou to reveal his heightened "demon mode" state. In later campaigns, Kou Yoku participated in the Battle of Gento against Qin. He reacted with shock and outrage upon learning of Prime Minister Shun Shin Kun's assassination, demanding answers in the capital. Promoted to general, he commanded 15,000 troops during the Juuko Arc under Ka Rin's orders to reinforce Chu against Qin's invasion. He re-engaged Tou during this conflict but was outmaneuvered when Tou bypassed him to strike Chu's headquarters. Following Qin General Kan Ki's death, Ka Rin tasked Kou Yoku with capturing Qin territories using 30,000 soldiers. Kou Yoku maintains significant relationships within Chu's military. His bond with Haku Rei is rooted in mutual battlefield trust developed over years of service. He respects but is unnerved by Shun Shin Kun's caustic nature. He openly dislikes Ka Rin's strategic approach to warfare, though he acknowledges her capabilities and refuses her advances despite offers of rewards. He views Tou as his personal nemesis and considers Shin, Mou Ten, and Ou Hon rivals against whom he measures his growth. Speculation exists regarding his lineage, as he shares the surname "Kou" and wields the *Bakuya Sword*, suggesting a potential connection to Kou En, the "Tiger of Chu" and supreme commander of Chu's military.