Kogoro Mouri is a private detective who operates the Mouri Detective Agency in Beika Town. He is the father of Ran Mouri and the estranged husband of Eri Kisaki, a highly successful lawyer. Before becoming a detective, he served as a police officer in the Tokyo Metropolitan Police Department's First Investigative Division under Inspector Megure. He left the police force around the time his wife moved out of the family home, and the two have lived apart for many years though they remain legally married. Kogoro attended Teitan High School alongside Eri and later graduated from Beika University, where he was the ace of the judo team.

Kogoro is presented as a deeply flawed but good-natured man. He is often lazy, boastful, and easily distracted by alcohol, gambling, and attractive women, particularly the pop idol Yoko Okino, whom he idolizes. He has an inflated sense of his own detective abilities and frequently makes hasty, erroneous accusations during investigations. Despite this, he possesses a strong sense of justice and becomes genuinely serious and effective when his daughter or wife is in danger. In those moments his observational skills and deductive reasoning sharpen, and he can solve cases on his own—sometimes even surpassing the efforts of those around him. He is also prone to fits of vanity and overconfidence, yet he can be deeply insecure about his marriage and his role as a father.

His primary motivation is maintaining his reputation as a famous detective, though he is unaware that his public success is built on the work of Conan Edogawa, the child form of Shinichi Kudo who lives in his home. Conan regularly tranquilizes Kogoro at crime scenes and uses a voice-changing device to impersonate him, presenting the correct conclusions while Kogoro is unconscious. Kogoro sincerely believes that he solves these cases in a trance state and proudly accepts the resulting fame, which he calls the sleeping Kogoro. This dynamic makes Kogoro an unwitting front for Conan’s investigations and allows the story to continue without exposing Conan’s true identity.

Kogoro’s relationship with his daughter Ran is central to his character. He can be neglectful and short-tempered, but he deeply loves her and will go to great lengths to protect her. With his wife Eri, he feigns disinterest but still harbors strong affection; he has attempted to reconcile and often acts protectively toward her, though their interactions typically devolve into argument. He is suspicious of Shinichi Kudo and disapproves of his closeness with Ran, though he acknowledges Shinichi’s intelligence. He treats Conan as an irksome but tolerated presence, occasionally showing grudging paternal care. He maintains a friendly, if strained, working relationship with Inspector Megure and other police officers, who have grown accustomed to relying on the sleeping Kogoro for difficult cases.

Over the course of the series, Kogoro’s character shows small signs of development. While he remains largely the same in his everyday behavior, he becomes slightly more aware of the peculiar circumstances of his success and occasionally voices suspicion, though he never pursues it deeply. He also demonstrates that when his pride or family is directly involved, he can be a capable investigator in his own right. His core traits—laziness, boastfulness, flirtatiousness, and underlying decency—persist, but his love for his family and his commitment to justice are consistently reaffirmed.

Kogoro possesses notable physical abilities. He is a master of judo, especially a powerful shoulder throw technique, and he taught the move to his wife. He is also an excellent marksman, a skill retained from his police days. These combat skills allow him to subdue criminals effectively when necessary. His deductive abilities are generally weak, but he has a good intuitive grasp of human emotions and motives, especially when he cares about the people involved. He also has some knowledge of police procedure and forensic basics from his former career, though he rarely applies them thoroughly.