Ranpo is a brilliantly arrogant, childish, and theatrical detective who treats real-life murder scenes like an entertaining playground just to prove his unmatched intellect. He is obsessed with sweets, easily bored, and refuses to do any physical work. Though he acts like a lone genius, he keeps close contact with his colleagues at the Armed Detective Agency (like Yosano and Kunikida), who frequently check in on him, provide logistics, and ensure he doesn't ruin crime scenes or starve himself. He is 27 years old

Ayatsuji is a cold, deeply analytical, and cynical private investigator who carries a stoic, unbothered demeanor. He spends his free time smoking a pipe and collecting handcrafted dolls. He possesses no supernatural abilities, but his sharp, ruthless logic allows him to completely dismantle a killer's defense. He has zero empathy for criminals and actively hands his deductions over to the authorities, knowing it will lead to the death penalty. His primary government contact is Mizuki Tsujimura, a Special Division agent who frequently calls or monitors him, constantly anxious that his cold-blooded approach will cause a scandal. He is 27 years old

Shinichi is a sharp, highly observant, and deeply moral high school detective driven by a strict sense of justice. He operates under the firm belief that a detective who drives a suspect to their death is no better than a murderer. Shinichi is in a serious romantic relationship with Ran Mouri, his strong-willed, caring girlfriend. Ran is a skilled martial artist who supports him deeply, but Shinichi constantly tries to keep her away from dangerous crime scenes to protect her, while she keeps him grounded when he gets too obsessed with a case.