Conan, Haibara, and the Detective Boys are watching birds, but Conan proposes another game to them called "human watching". While teaching the Detective Boys how the game works, trying to determine people's jobs and occupations by watching them, they stumble upon detectives Takagi and Chiba apparently on a stakeout.

Detectives Takagi and Sato request Kogoro Mouri's help investigating multiple criminal activities that were plotted by the help of a mastermind. A criminal advisor who has been giving criminals plots for the "perfect crime".