Detective Wataru Takagi serves as a sergeant and detective within the Tokyo Metropolitan Police Department's Criminal Investigation First Division. When Lupin III exhibits unusual behavior during the Cherry Sapphire case, the Tokyo Police consult Inspector Zenigata. Takagi volunteers with his partner, Miwako Sato, to assist Zenigata in guarding the valuable jewel. During the security operation, Lupin III successfully impersonates Takagi to bypass the guards and steal the Cherry Sapphire. Sato's previous admission of having harbored a childhood crush on Lupin III introduces a layer of tension to the situation, though Takagi's personal reaction to this revelation remains unstated. The Cherry Sapphire case represents the sole documented instance of Takagi's involvement within this specific narrative.