Kou, a prominent figure in the series, emerges from a humble merchant background to enter Qin's royal harem. During the Escape from Zhao arc, she serves as an attendant and captures King Ei Sei's interest, leading to frequent non-intimate summons. Her deepening affection culminates in a love confession, prompting Ei Sei to reveal his traumatic history and forging a bond of trust between them. In the Assassination Plot arc, Kou overhears treasonous discussions between Queen Mother and Chancellor Ryo Fui. While attempting to expose the conspiracy, she suffers a near-fatal stabbing. Defying her injuries, she survives long enough to relay crucial intelligence to Ei Sei, enabling him to dismantle the plot. This act cements her reputation for fierce loyalty. Her role evolves during the Coalition Invasion arc as her relationship with Ei Sei turns intimate, resulting in pregnancy. Amidst escalating warfare, she fears for Ei Sei and Qin's survival. Before the Battle of Sai, they share a poignant farewell with promises of reunion. Post-victory, she gives birth to their daughter Rei. Later arcs depict Kou nurturing Rei and partaking in daily life, such as snow play during the Western Zhao Invasion. Physically, Kou is petite with dark brown twin pigtails, green eyes, and an unassuming appearance that occasionally reveals subtle allure. A scar marks her abdomen from the assassination attempt. Shy and modest with lingering self-doubt, she demonstrates quiet resilience when defending Ei Sei or their family. Her calming presence provides Ei Sei emotional stability during turmoil. A separate character named Kou, a soldier in the Hi Shin Unit, hails from Jouto Village alongside Shin, Hyou, Bi Hei, Bi Tou, and Kei. Enlisting via emergency draft, he fights in pivotal battles like Bayou and Sanyou, rising to 100-man commander through proven reliability. This Kou possesses exceptional strength, endurance, and spearmanship, honed through relentless campaigns. He masters joint-locking and Sound Muffling techniques from Kyou Kai, showcasing combat adaptability. Blunt yet honest, he harbors profound loyalty to comrades and profound devotion to his widowed mother, driving his military service. His dynamic with Kyou Rei begins antagonistically when she threatens him after his lifesaving intervention during the Shiyuu Conflict. Undeterred, Kou patiently builds rapport by sharing worldly knowledge and offering steadfast support. Romantic feelings blossom, leading to a marriage proposal post-Hango Campaign. His evolution from village youth to battle-hardened warrior underscores his integral role in the Hi Shin Unit's growth.