"Detektiv Conan: The Private Eyes' Requiem" is a feature-length anime film that centers around a high-stakes mystery involving a group of private detectives. The narrative begins with Conan Edogawa, a brilliant young detective whose true identity is the high school detective Shinichi Kudo, attending a private detective convention hosted by a mysterious individual known only as "K." The event gathers some of Japan's most renowned private detectives, including Kogoro Mouri, Ran Mouri, and Heiji Hattori, among others. The participants are invited to solve a series of puzzles and challenges, with the promise of a substantial reward for the winner.

As the detectives engage in the competition, they are suddenly confronted with a series of life-threatening situations. The challenges escalate into a dangerous game orchestrated by K, who reveals a personal vendetta against the detectives. K accuses them of being complicit in a past tragedy that resulted in the death of a loved one. The detectives must now work together to unravel the mysteries presented to them while also uncovering the truth behind K's motives.

The plot thickens as Conan and his allies discover that K has planted bombs throughout the city, with the detonation tied to the progression of the detectives' investigation. The stakes are raised further when it becomes clear that K has a personal connection to one of the detectives, adding a layer of emotional complexity to the unfolding events. Conan, using his sharp intellect and deductive skills, takes the lead in deciphering the clues and outsmarting K's elaborate schemes.

Key characters include Conan Edogawa, whose youthful appearance belies his exceptional detective abilities; Kogoro Mouri, a bumbling yet occasionally insightful detective; Ran Mouri, Kogoro's daughter and Conan's close friend; and Heiji Hattori, a skilled detective from Osaka who often collaborates with Conan. The film also introduces K, the enigmatic antagonist whose motivations and methods drive the central conflict.

The narrative builds to a tense climax as the detectives race against time to prevent the bombs from detonating and to confront K. The resolution hinges on Conan's ability to piece together the final clues and expose K's true identity, bringing the dangerous game to an end. The film combines elements of mystery, suspense, and action, maintaining a focus on the intellectual and emotional challenges faced by the characters as they navigate the intricate plot.