Detective Kazunobu Chiba, commonly referred to as Detective Chiba, is a member of the Metropolitan Police Department's Second Violent Crimes Investigative Division, Section Three. At the time of the events depicted, he is approximately twenty-four to twenty-five years old. In his early appearances, he was depicted with a leaner build, but he has since been consistently portrayed as an overweight character, a physical trait that sometimes serves as a source of gentle humor.

Chiba attended Teitan Elementary School, where he was a member of the broadcasting committee and developed a lifelong passion for tokusatsu, which are live-action special effects shows such as Kamen Yaiba and Gomera. His apartment is known to be decorated with numerous figurines of these characters. He also has a notable, somewhat quirky habit of checking video tapes to see if they have been rewound, a practice he believes he picked up from an older brother who worked at a video rental store.

Personality-wise, Chiba is generally light-hearted and serious when the situation demands it. He has a strong moral compass and is deeply committed to upholding the law, believing that anyone who breaks the rules must be punished, including himself. This principle was demonstrated when he once scolded a young woman for a minor traffic violation, an act that profoundly influenced her. He is also a loyal and supportive colleague, particularly towards his friend and fellow detective, Wataru Takagi. Chiba is one of the few officers who actively supports Takagi's romantic pursuit of their colleague, Miwako Sato, and does not participate in the schemes of others to sabotage their relationship.

Chiba has a significant, though complicated, relationship with Naeko Miike, a patrol officer in the traffic department. They were classmates in elementary school, and Chiba developed feelings for her. Before her family moved away, he wrote her a love letter, and she responded by hiding a message on a video cassette, believing his childhood habit of sweating would help him find it. He never discovered the message, and when Naeko later transferred to Tokyo and joined the police force, he did not recognize her. She has been attempting to get him to remember her on his own.

In the feature film, Detective Conan: Quarter of Silence, Detective Chiba appears as part of the police team led by Inspector Megure. His role within the story is consistent with his function in the wider series, where he assists in the investigation and provides logistical support at crime scenes. The movie, which involves an explosion at a new subway line that leads Conan and his friends to a snow-covered village, showcases Chiba working alongside his colleagues from the Tokyo Metropolitan Police to unravel the events of a tragic incident from eight years prior.