Mitsuko Asatani is a special investigator dispatched from Tokyo Police Headquarters to assist local authorities in the pursuit of the art‑thief trio known as Cat's Eye. She is an elite officer of the Tokyo Metropolitan Police Department, recognized for her sharp intellect and cunning nature. Her demeanor is stern and direct, and she is consistently well‑informed and studious in her approach to cases. Asatani’s primary motivation is to capture Cat’s Eye, and she becomes one of the first individuals to suspect that Hitomi Kisugi is the group’s leader, though she is never able to gather definitive proof. She harbors a subtle, unacknowledged romantic interest in Hitomi’s fiancé, Toshio Utsumi, a detail more prominent in the original manga than in the animated adaptations.

Asatani possesses exceptional physical abilities. She is an expert markswoman, having won the All‑Japan Air Pistol Championships, and is highly proficient in martial arts, holding a fourth‑degree black belt in karate and a second‑degree black belt in judo. These skills make her a formidable opponent, physically able to challenge Hitomi in direct confrontation. She is also noted for her striking appearance and was once crowned a beauty queen during an investigation involving Cat’s Eye. Her primary weakness is her reliance on prescription glasses; without them she is practically blind. Throughout the story, Asatani remains a persistent and capable investigator whose role as a foil to the Kisugi sisters adds tension to the narrative. She does not undergo major personal change, but her unwavering dedication and acute observations keep her a constant threat to the thieves.