Detective Tamagawa is a minor character who appears in the special episode A Challenge Letter to Shinichi Kudo: Prologue Until Goodbye. He is a policeman serving with the Kanagawa Prefectural Police. His first name is not disclosed in the available information.

Tamagawa is characterized as an exceptionally stubborn and hard-headed individual. His personality is noted to be extremely rigid, to the point where he is described as being ten thousand times more stubborn than the familiar Inspector Megure from the Tokyo Metropolitan Police. This inflexibility has earned him the nickname the non-negotiable, Everest of the prefectural police, highlighting his reputation as an immovable force who does not yield to pressure or persuasion.

In the story, his primary role is to lead a police investigation. True to his reputation, he refuses to allow the famous high school detective Shinichi Kudo and the private investigator Kogoro Mouri to participate in or assist with the case he is handling. This action demonstrates his territorial nature and disdain for outside interference, even from individuals with renowned deductive skills. No information is available regarding his background, motivations for becoming a police officer, character development throughout the series, key relationships with other recurring characters, or any specialized notable abilities.