Naoya Ushio is a detective in the Tokyo Metropolitan Police Department's Public Safety Division 5, serving in C Squad. He is also a double agent secretly working for the CCC, an organization that schemes to eliminate devils, and is known within that group by the code name Zero Five. He stands 1.68 meters tall, with black hair and brown eyes, and his birthday is September 23. Ushio is portrayed as a diligent and hardworking officer who is deeply dedicated to his job, often sacrificing his personal life to solve cases. He maintains a calm and composed demeanor even in dangerous situations, and he is known for his sharp mind and attention to detail, which aid his investigations. As the story progresses, his involvement with devils increases; he begins to believe that not all devils are inherently evil and that peaceful coexistence between humans and devils may be possible. This belief leads him to act as a mediator between the two groups, working to bridge the divide and find a resolution to their conflict. He frequently interacts with the main characters, including Tsukasa Taira and the half-devil detective Yuki Anzai, and plays a supporting role in the investigation of devil-related crimes and the conspiracy surrounding the CCC.