A former police detective with a strong sense of justice, Hideyuki Makimura worked alongside Saeko Nogami before resigning due to an unspecified incident. After leaving the force, he partnered with Ryo Saeba to form the City Hunter team, handling assignments, client confirmations, and information gathering, often attempting to manage Ryo's impulsive and womanizing tendencies.

His father, a police officer, brought home the infant Kaori, leading Hideyuki to become her adoptive older brother despite no biological relation. He deeply cared for Kaori and planned to reveal the truth about their familial connection on her twentieth birthday. This plan was interrupted when he was murdered by the criminal syndicate 'Union Teope' in the manga, or its affiliated group 'Red Pegasus' in the anime adaptation. His dying request to Ryo was to protect and care for Kaori, leaving his small revolver to her as a memento. His favorite firearm was the Colt Roman MK III revolver.

Hideyuki favored the first-generation Mazda Carol for transportation in the manga, while the anime depicted him driving a yellow Volkswagen. Flashback sequences in the anime associated his character with an instrumental version of Bruce Hornsby’s "The Way It Is," later revealed as his preferred song during an anime-exclusive storyline involving the Red Pegasus syndicate.

He maintained a calm, responsible, and protective demeanor, contrasting sharply with Ryo’s personality. Hideyuki was depicted as neat, capable of household chores, and dedicated to both his work and family. A minor police officer named Hirotaka Kitao appeared in the manga bearing a strong resemblance to him. In international adaptations, his name was localized as "Jeff Mancinelli" in Italy and "Tony Marconi" in France. No concrete information exists regarding his appearance or role in *City Hunter: Death of the Vicious Criminal Ryo Saeba*.