Kou Yoku, known as the Thunder, serves as a general in the Chu military. Though his early life remains largely unknown, he joined the Chu military in his early teens and rapidly ascended to 100-man commander due to exceptional combat talent. He spent years touring Chu's southern battle lines alongside his best friend Haku Rei and their commanding general Rin Bu Kun, developing deep respect for Rin Bu Kun's leadership and relying on Haku Rei's archery in battle. Clean-shaven with shoulder-length, greasy black hair and a muscular frame covered in scars, Kou Yoku combines a rude, laid-back demeanor with intense combat enthusiasm, boasting the loud arrogance common among Chu soldiers. While sharing his rival Shin's brashness, he demonstrates greater pragmatism and intelligence in tactical situations, operating primarily as an instinctual fighter. Wielding the legendary Bakuya Sword, Kou Yoku ranks among the series' most powerful swordsmen. Official stats reflect his combat focus: 91 strength, 86 command, 78 intelligence. He commands the formidable Kou Yoku Army, directly under Great General Ka Rin after his unit's absorption into her command following Rin Bu Kun's death. Key relationships define him: - His bond with Haku Rei involves mutual life-saving trust forged over years of shared battles; Kou Yoku fiercely defends Rei against threats. - He revered Rin Bu Kun as the ideal general; Rin Bu Kun's death during the Coalition Invasion Arc devastated Kou Yoku, driving him to swear vengeance against Qin Great General Tou. - Though respecting Prime Minister Shun Shin Kun, Kou Yoku found his caustic nature unnerving and reacted with outrage to his assassination. - He maintains contentious dynamics with Ka Rin, disliking her strategic style but acknowledging her capability; he accepts promotions under her command while refusing her romantic advances. - He views Qin commanders Shin, Mou Ten, and Ou Hon as rivals, using them to measure his growth, and considers Tou his nemesis. His story progression includes: - An initial encounter with Shin's Hi Shin Unit at the Qin-Chu border during the Sanyou Aftermath Arc, taunting Qin forces before a brief clash with Shin. - Participation in the Coalition Invasion Arc under Rin Bu Kun's command, dueling Mou Ten and Ou Hon before witnessing Rin Bu Kun's death at Tou's hands, leading to tearful vows of revenge. - Promotion to 5000-man commander by Ka Rin during the same campaign, strategically engaging Tou to delay him while surrounding him with troops. - Later involvement in southern campaigns against Qin, including the Battle of Gento. - A panicked return to Chu's capital after Shun Shin Kun's assassination demanding answers. - Deployment as a general alongside Haku Rei during the War of the Three States Arc to reinforce Juuko against Qin's Mou Bu, where he confronted Tou again but failed to halt Tou's advance on Chu's headquarters. Speculation about a potential familial link with Tiger of Chu Kou En persists due to their shared surname and military prominence, though unconfirmed. Kou Yoku represents Chu's next generation of military leadership, driven by personal loyalties, vengeance, and competitive rivalry with Qin's rising commanders.