In the anime film Sengoku Basara: Samurai Kings: The Last Party, Ieyasu Tokugawa is portrayed as a young man of strong convictions and considerable physical prowess, who has cast aside his youthful appearance and heavy reliance on his retainer to become a central figure in the struggle to unify Japan. His background is rooted in the turbulent era of the warring states, having once served under the brutal Toyotomi Hideyoshi. Disillusioned by Hideyoshi's oppressive lust for power, Ieyasu ultimately rebelled and killed him, an act that forms the core of his present conflict and guilt.

Ieyasu's personality is defined by his idealism and his unwavering belief in the power of bonds, or kizuna, as the true means to achieve lasting peace. He is a caring and respectful leader who seeks to unite the country not through fear and force, but through trust and mutual alliance. Despite this benevolent exterior, he is a complex figure who carries a heavy burden of doubt and guilt. Aware of the hypocrisy in waging war to create peace, he puts on a brave front as a benevolent leader, masking his inner conflict and sorrow over the actions he has had to take, particularly the killing of Hideyoshi and the consequent hatred he must bear. His primary motivation is the establishment of a peaceful and prosperous nation, a goal he pursues with a direct and earnest, if sometimes naive, determination.

In the story of The Last Party, Ieyasu serves as the leader of the Eastern Army, actively seeking to recruit allies from various factions to oppose the Western Army led by Ishida Mitsunari. His role is that of a unifier and a reluctant combatant who would rather win others to his cause through words and shared ideals than through violence. A key aspect of his character is his fraught relationship with Mitsunari, a former friend and fellow retainer of Hideyoshi who now despises Ieyasu, believing him to be a traitor and murderer. Ieyasu accepts this hatred, even deliberately lying about killing Hideyoshi, to give Mitsunari a reason to live and channel his grief into purpose. Other significant relationships include his loyal bond with the powerful mechanized warrior Honda Tadakatsu, whom he once relied upon heavily but now fights alongside as an equal, and a deep-seated friendship with the pirate Chosokabe Motochika, which is tested by the shifting political landscape.

Ieyasu undergoes notable development, having transformed from an inexperienced and often kidnapped child known by his childhood name "Takechiyo" into a mature and formidable leader. His evolution is symbolized by his combat style; in his youth, he wielded a double-bladed spear, but by the events of The Last Party, he fights with his fists, using brass knuckles. This choice is deliberate, as he believes in feeling the pain of battle to truly understand the cost of war and to share in the struggle of his men. Throughout the film, he grapples with the moral ambiguities of his path, questioning if his methods make him any different from the tyrants he opposes, yet he remains steadfast in his quest for unity through interconnected bonds. His notable abilities include incredible punching power, with many of his techniques charging up for devastating effect. He can summon a powerful battle aura for attacks like the Tokugawa Might, can crush the ground with a punch, and possesses a powerful headbutt technique. When he pulls up the hood of his jacket, it allows him to charge his attacks more quickly, signifying his focus in battle.