Miwako Satou is a police assistant inspector and detective in the Tokyo Metropolitan Police Department's First Investigative Division. Her decision to become a police officer was shaped by the death of her father, Masayoshi Satou, who was killed in a traffic accident while transporting a bank robber when she was young. She carries a strong sense of justice and is known for her fearless, sometimes reckless approach to dangerous situations. Despite her tough exterior, she is kind and friendly, especially toward Conan Edogawa and the Detective Boys, whose judgment she trusts implicitly. Her natural attractiveness has made her the object of affection for many male officers, but her heart belongs to her colleague and partner, Wataru Takagi, with whom she shares a romantic relationship that deepens over the course of the series.

In The Bride of Halloween, Satou is the bride at a wedding ceremony held at Shibuya Hikarie. The ceremony is interrupted when an armed intruder bursts in, and Takagi is injured while protecting her. This event forces Satou to confront the trauma of her first love, Jinpei Matsuda, a bomb disposal expert who was killed in an explosion years earlier. The case that unfolds involves a serial bomber and a plot threatening the entire Shibuya Halloween festival. Satou's personal history with Matsuda and her current commitment to Takagi are central to her emotional journey in the film. She demonstrates courage, sharp investigative instincts, and a willingness to put herself in harm's way to protect others. Her combat skills are formidable; she is proficient in jujitsu and wrestling, and she is an exceptional driver, known among street racers as the Silver Witch for her aggressive and skillful handling of her Mazda RX-7. She is also an accurate markswoman. Throughout the story, Satou's loyalty to her colleagues and her determination to see justice done drive her actions, and her relationship with Takagi provides a grounding emotional core amid the high-stakes investigation.