"Sengoku Basara - Samurai Kings: The Last Party" is a feature-length anime film that serves as a continuation of the "Sengoku Basara" series, set in a fictionalized version of Japan's Sengoku period. The story revolves around the intense rivalry and eventual alliance between two powerful warlords, Date Masamune and Sanada Yukimura, as they face a new and formidable threat to the nation.

The narrative begins with the unification of Japan under the rule of Toyotomi Hideyoshi, who seeks to impose his iron-fisted control over the land. His oppressive regime sparks resistance from various factions, including Masamune and Yukimura, who initially clash due to their differing ideals and methods. Masamune, known as the "One-Eyed Dragon," is a brash and ambitious leader with a modern, Western-influenced approach to warfare. Yukimura, the "Crimson Armor," is a passionate and loyal warrior who fights with traditional Japanese values and unwavering determination.

As the conflict escalates, the warlords discover that Hideyoshi's ambitions are fueled by a mysterious and powerful force, which threatens to plunge the nation into chaos. This revelation forces Masamune and Yukimura to set aside their differences and form an uneasy alliance. Together, they rally other notable figures of the era, including Tokugawa Ieyasu, Oda Nobunaga, and Ishida Mitsunari, to confront the growing threat.

The film culminates in a climactic battle at Osaka Castle, where the combined forces of the warlords face off against Hideyoshi's overwhelming army. The confrontation tests their resolve, strategies, and bonds, as they fight not only for their survival but also for the future of Japan. The story emphasizes themes of unity, sacrifice, and the enduring spirit of the samurai, while staying true to the over-the-top action and dramatic flair characteristic of the series.

Key characters include Date Masamune, whose dual-wielding swords and rebellious nature make him a standout figure; Sanada Yukimura, whose fiery passion and loyalty drive much of the emotional core; and Toyotomi Hideyoshi, whose descent into tyranny and connection to the mysterious force serve as the central conflict. Supporting characters like Tokugawa Ieyasu and Ishida Mitsunari provide additional depth to the political and personal dynamics of the story. The film concludes with a resolution that ties together the fates of the characters while leaving room for the ongoing legacy of their struggles.