Ei Sei, born Ying Zheng, serves as the 31st King of Qin. His early childhood unfolded as a political hostage in Zhao after his father, King Sou Jou, abandoned him during an escape from Kantan. During this exile, Zhao citizens, resentful of his Qin heritage, subjected him to severe abuse and torture, inflicting deep psychological trauma. His mother, the former Zhao dancing girl Bi Ki, also attempted to kill him multiple times. This brutal period extinguished his ability to feel physical sensations and left him haunted by inner demons, believing himself tormented by the ghosts of Chouhei. Shi Ka, a Zhao black-market merchant, restored his humanity by sacrificing her life to aid his escape to Qin. Initially cold and distrustful, Ei Sei displayed ruthlessness in eliminating threats, unhesitatingly killing the assassin Jo Kan despite Shin's pleas for mercy. Yet he showed care for loyal followers, carrying an exhausted Shin without complaint. His relationship with Shin evolved from viewing him as a useful "sword" for his ambitions to deep mutual trust and reliance, solidified during the battle against his half-brother Sei Kyou to reclaim the Qin throne. Ei Sei entrusted Shin with critical missions, like defending the royal hall, marking significant personal growth and the capacity for genuine bonds. Crowned king at 22 during a Kinen Palace ceremony (Season 4, Episode 17), Ei Sei had nominally held the throne since age 13. His reign focused on unifying China's warring states under Qin to end the 500-year Warring States period. He pursued this through military conquest and establishing a legalist system, intending to dissolve state borders, eliminate warfare, and enforce equality under centralized law. This vision clashed with alternatives: Riboku advocated a multi-state alliance, while Ryo Fui proposed economic prosperity. Ei Sei acknowledged his methods would cause massive bloodshed but believed it his destiny as a monarch born in an era of warfare to bear the costs for lasting peace. Ei Sei's relationships reveal contrasting facets. He deeply respected advisor Shou Bun Kun, relied on General Heki as a factional symbol, and formed a strategic alliance with Yo Tan Wa after aligning their unification dreams. His marriage to concubine Kou evolved from formality to genuine affection; she bore his adored daughter Rei, despite her frail health. His son Fusu received no documented interaction. His dynamic with half-brother Sei Kyou remained fraught with mutual disdain, though posthumous respect emerged after Sei Kyou's change of heart. His mother, the Queen Mother, continued opposing him, establishing the rival State of Ai. In combat, Ei Sei proved himself a capable swordsman, trained in Qin's warrior traditions. He beheaded assassins like Jo Kan with single strikes and fought on the front lines during the Battle of Sai, wearing distinctive golden armor with a dragon motif. His leadership during the Coalition Invasion rallied civilians to defend Sai, showcasing his oratory skills and resolve. These traits, combined with his charisma and resilience, drew parallels to his ancestor, the "God of War" King Shou. Historically framed as a future tyrant, Ei Sei's methods laid the groundwork for Qin Shi Huang's later-known policies: enforcing strict legalism, suppressing rival philosophies like Confucianism, and erasing cultural differences. The narrative acknowledges his unification legacy, while ending warfare, would involve brutality such as scholar purges and forced labor—a trajectory established but not yet fully realized.