Miyako Tomaru is a detective specializing in "phantom cases," unexplained supernatural phenomena plaguing Kyuto. Initially skeptical of Mayuki Hyuuga's abilities upon their first meeting, she questions his methods and value. This skepticism fades after witnessing his capabilities during investigations, leading to a respectful professional relationship. Information suggesting Mayuki is in danger consistently prompts her concern for his safety.

She primarily investigates alongside her partner, Inogami Ryūsuke. Their work blends conventional police methods with confronting the supernatural elements central to their cases. Despite operating in a world of espers and supernatural combatants, Miyako demonstrates significant physical competence and investigative skills, exemplified by her effective subduing of a hypnotized terrorist during an early case.

Her effectiveness faces limitations against entities like the antagonist Byakko, who possesses supernatural powers. Such encounters reveal her vulnerability to threats beyond normal human capabilities, leading colleagues like Inogami to acknowledge the dangers inherent in facing powers they cannot fully comprehend or counter. Seiran Shinano and others connected to the Hyuga and Shinano families deliberately withhold deeper supernatural knowledge from her, such as the existence of "Aya" (puppet warriors) or the true nature of the phantom cases, aiming to shield her from greater dangers.

Miyako's character development remains centered on her professional role, focusing on her evolving relationship with Mayuki and her partnership with Inogami.