Ran Mouri is a central figure in the anime Detective Conan. She is introduced as a sixteen-year-old high school student in class 2-B at Teitan High School, where she serves as captain of the karate club. She is the daughter of Kogoro Mouri, a private detective and former police officer, and Eri Kisaki, a skilled lawyer. Her parents have been separated since she was seven years old, and a significant part of her emotional life revolves around her hope of reconciling them, even though their mutual stubbornness makes that goal difficult to achieve. Ran lives with her father above the Mouri Detective Agency and, because Kogoro is often careless with money and neglectful of daily responsibilities, she has effectively taken charge of the household. She manages the family finances, does the cooking and cleaning, and looks after clients who visit the agency.

Ran is the childhood friend and romantic partner of Shinichi Kudo, a gifted high school detective who disappears early in the story after being shrunk to the size of a child by a criminal organization. In his new form, he lives with Ran under the name Conan Edogawa, and while she accepts him as a distant relative and grows to treat him like a younger brother, she does not know that Conan and Shinichi are the same person. Over the course of the series she occasionally suspects Conan's true identity, but she is repeatedly convinced otherwise, and she ultimately believes that Shinichi is simply away working on an important case. Her decision to wait for his return, trusting his promise despite the loneliness and worry it causes her, is a defining part of her character.

In terms of personality, Ran is compassionate, patient, and nurturing, with a strong and idealistic sense of justice. She cares deeply for the people around her and takes on a protective, almost maternal role in her household, keeping Conan safe and trying to keep her father in line. At the same time, she has a forceful side. When she is angered she can be intimidating, and she is prone to impulsive, hot-blooded reactions, especially when she feels someone she loves has been harmed or deceived. This combination of jumping to conclusions and being willing to use physical force has sometimes created misunderstandings. She is also fiercely loyal and, in early stories, could become intensely jealous if she suspected Shinichi of being interested in someone else, though later developments lead her to trust him more. Her courage is considerable. She remains composed in genuinely dangerous situations, such as being threatened with a gun or trapped in a fire, and she values human life deeply, to the point of saving even someone who had threatened her. That principle is shown most clearly during a trip to New York, when she instinctively rescues a serial killer in disguise from falling to her death. Despite her bravery, she has an intense fear of the supernatural, avoids horror-themed situations, and reacts to sudden shocks such as discovering dead bodies. She is also known for crying easily, tends to be shy and self-conscious about expressing her romantic feelings, and is humble about her own appearance, often oblivious to the attention other men give her.

Ran is highly skilled in karate, which she began practicing at around ten years old after being inspired by watching a national champion. By the time the series begins, she is one of the strongest fighters in the story, having won championships at the prefectural and Kanto level. Her physical abilities go beyond ordinary athleticism, allowing her to break doors, damage solid objects with her strikes, and take down armed criminals, and she has demonstrated sharp reflexes and good instincts under pressure. She also has practical domestic talents, particularly cooking, and she is perceptive and emotionally intelligent in ways that frequently place her at the heart of the story's human drama.

Her key relationships shape much of her arc. Her bond with Shinichi is the emotional center of her character, evolving from childhood friendship to love, which she fully realizes during a trip to New York. In London, Shinichi confesses to her, and later, during a school trip to Kiyomizu-dera, she answers by kissing him on the cheek, confirming their relationship. Her friendship with Sonoko Suzuki, a wealthy classmate who constantly teases her about Shinichi and supports her, provides both humor and stability. With her father, Kogoro, she is affectionate but firm, acting as the responsible figure in the household, while her relationship with her mother, Eri, is marked by love and the quiet sadness of their separation. Her care for Conan is genuine and maternal, and she frequently rescues him from danger, even as he works secretly to protect her from the threats he cannot reveal.

Over the course of the series, Ran develops from a capable but somewhat sheltered teenager into a more emotionally resilient young woman. Her patience in waiting for Shinichi, her growing confidence in her relationship with him, and her willingness to face dangerous situations all demonstrate her maturation, while her compassion and determination remain constant. She is one of the story's main protagonists and serves as the emotional anchor of the cast, representing the ordinary life and personal bonds that the more extraordinary detective work is meant to protect.