"Lupin III vs. Detective Conan" is a crossover special that brings together two iconic franchises: the suave master thief Arsène Lupin III and the brilliant young detective Shinichi Kudo, also known as Conan Edogawa. The story unfolds when a priceless jewel, the Cherry Sapphire, is stolen during a high-profile event in the fictional European country of Vespania. The theft is initially blamed on Lupin III, but he claims innocence and sets out to clear his name. Meanwhile, Conan, who happens to be in Vespania with his friends, becomes involved in the investigation.

The narrative intertwines the two protagonists as they navigate a complex web of intrigue involving the Vespanian royal family, a shadowy organization, and a series of high-stakes heists. Lupin III, accompanied by his loyal partners Daisuke Jigen and Goemon Ishikawa, employs his signature wit and cunning to outmaneuver both the authorities and the true culprits. Conan, using his sharp deductive skills and advanced gadgets, works to uncover the truth behind the theft and the motives of those involved.

As the story progresses, Lupin and Conan find themselves in a tense game of cat and mouse, each trying to outsmart the other while also collaborating to thwart a larger conspiracy. The dynamic between the two leads is central to the plot, blending Lupin's playful, roguish charm with Conan's methodical and analytical approach. Supporting characters from both series, including Inspector Zenigata, Fujiko Mine, and the members of the Detective Boys, contribute to the unfolding events, adding depth and familiarity for fans of either franchise.

The special culminates in a high-octane climax where Lupin and Conan must join forces to prevent a catastrophic event tied to the Cherry Sapphire. The resolution highlights their mutual respect and the unique strengths each brings to the table, offering a satisfying conclusion to their unlikely partnership. The crossover maintains the distinct tones of both series, balancing Lupin's adventurous heist elements with Conan's mystery-driven narrative, creating a cohesive and engaging story for fans of both franchises.