"Lupin III: Island of Assassins" is a direct-to-video anime special that centers on the exploits of the master thief Arsène Lupin III and his team. The story begins with Lupin and his partner Daisuke Jigen infiltrating a high-security facility to steal a valuable artifact. During the heist, they encounter a mysterious woman named Aisha, who is revealed to be a skilled assassin. Aisha is on a mission to retrieve the artifact for her employer, a powerful figure known as the Professor. The artifact, a golden statuette, is tied to a larger conspiracy involving a secretive island inhabited by elite assassins.

The narrative takes a dramatic turn when Lupin and Jigen are captured and brought to the island, which serves as a training ground for assassins under the Professor's control. The island is a heavily fortified location where the assassins are conditioned to eliminate targets without hesitation. Aisha, despite her initial antagonism, begins to question her loyalty to the Professor after witnessing Lupin's resourcefulness and charisma. Meanwhile, Lupin's longtime allies, Goemon Ishikawa and Fujiko Mine, become involved in the plot as they attempt to rescue Lupin and Jigen. Fujiko, in particular, plays a pivotal role by infiltrating the island undercover, using her charm and cunning to gather intelligence.

As the story progresses, the true nature of the artifact is revealed: it contains a hidden map leading to a vast treasure hidden on the island. The Professor's ultimate goal is to use the treasure to fund a global network of assassins, furthering his control over the criminal underworld. Lupin, ever the opportunist, sees this as a chance to outwit the Professor and claim the treasure for himself. The climax involves a series of high-stakes confrontations, including a showdown between Lupin and the Professor, as well as Aisha's internal struggle between her loyalty and her growing admiration for Lupin's ideals.

The special maintains the signature blend of action, humor, and intrigue that defines the Lupin III franchise. The characters' dynamics are central to the plot, with Lupin's wit and audacity contrasting with Jigen's stoic professionalism, Goemon's disciplined swordsmanship, and Fujiko's unpredictable nature. Aisha's character adds depth to the narrative, serving as both an antagonist and a reluctant ally. The story concludes with Lupin and his team narrowly escaping the island, having thwarted the Professor's plans but leaving the treasure's fate ambiguous, a nod to the series' recurring theme of Lupin's elusive victories.