"Lupin the IIIrd: Jigen's Gravestone" is a 2014 anime film that serves as a spin-off of the "Lupin III" franchise, focusing on the character Daisuke Jigen. The story is set in the fictional Eastern European country of East Doroa, where Lupin III and his partner Jigen plan to steal a rare and valuable treasure: a superweapon known as the "Little Comet." This weapon, capable of firing bullets at supersonic speeds, is guarded by a highly skilled and enigmatic assassin named Yael Okuzaki, who is determined to eliminate anyone who threatens the weapon's security.

The narrative begins with Lupin and Jigen infiltrating a heavily fortified military base to steal the Little Comet. However, their heist is interrupted by Yael, who effortlessly outmaneuvers them. Jigen, known for his unparalleled marksmanship, is particularly challenged by Yael's speed and precision, which surpass even his own abilities. This encounter leaves Jigen shaken, as he realizes he may have met his match. The rivalry between Jigen and Yael becomes a central focus, driving much of the film's tension.

As the story progresses, Lupin and Jigen uncover the truth about Yael's origins. Yael was once a soldier who underwent experimental enhancements to become a perfect assassin, but these modifications have left him with a limited lifespan. His mission to protect the Little Comet is tied to a personal vendetta against those who exploited him. Meanwhile, Lupin and Jigen must navigate a web of betrayal and deception involving East Doroa's corrupt government officials, who are also vying for control of the superweapon.

The film culminates in a high-stakes showdown between Jigen and Yael, set against the backdrop of a crumbling fortress. The confrontation is both a test of skill and a battle of ideologies, as Jigen grapples with the idea of facing an opponent who is not only his equal but also a tragic figure shaped by forces beyond his control. The resolution of their duel carries significant consequences for both characters and underscores the themes of mortality and legacy that permeate the story.

Throughout the film, Lupin's trademark wit and resourcefulness provide a counterbalance to the darker, more introspective elements of Jigen's journey. The dynamic between Lupin and Jigen remains a cornerstone of the narrative, highlighting their deep mutual respect and camaraderie. Supporting characters, such as Inspector Zenigata, also make appearances, adding layers to the story's intricate plot. "Lupin the IIIrd: Jigen's Gravestone" delivers a tightly paced, action-driven narrative that explores the complexities of its central characters while staying true to the adventurous spirit of the "Lupin III" series.