Sai Taku, a native of Yan, rose to prominence as chancellor under King Sho of Qin decades before the series' events. Later joining Lü Buwei’s inner circle as one of the Four Pillars, he served as Qin’s foremost diplomat, operating primarily in Yan. Though advanced in years and lacking physical might, he commanded exceptional leadership, intellect, and diplomatic acumen, his mastery of statecraft proving instrumental in shaping political strategies. His career hinged on cultivating alliances with foreign leaders, most notably the King of Qi, where his charm and renown forged critical bonds. During a historic summit between Ei Sei and Qi’s ruler, Sai Taku orchestrated negotiations to unify the warring states under a legalist system advocating equality over hereditary privilege. This encounter unveiled his own abandoned aspirations for unification, reflecting a lifetime navigating the era’s intricate power dynamics. Evolving allegiances led Sai Taku to embrace Ei Sei’s vision upon recognizing its potential to transcend partisan interests. His crowning achievement—brokering Qi’s neutrality and conditional surrender—secured a strategic foothold for Qin’s unification aims. He succumbed to age shortly thereafter, content in having steered history’s course. The King of Qi, his longtime counterpart, honored his legacy by protecting his remains during ensuing conflicts. Renowned for his ever-present smile and distinctive “Hyohyohyo” chuckle, Sai Taku blended geniality with calculated pragmatism. Though devoid of martial prowess, his strategic brilliance and diplomatic mastery epitomized the cerebral strategist, reshaping alliances through words rather than warfare.