Keiichiro Nagumo is a 35-year-old former genius boy detective who once gained national recognition for solving difficult cases in his youth, but as an adult his glory has faded and his body can no longer keep up the way it used to. He now runs a small, barely functioning detective agency, rarely receiving clients and often spending his days looking tired, disillusioned, and physically worn down. Despite his exhaustion and declining stamina, Nagumo still retains the sharp deductive instincts that made him famous, instantly shifting into a focused, perceptive mode whenever a case demands it. He frequently shows frustration and reluctant involvement in investigations, but his long experience and natural talent allow him to solve mysteries with surprising precision—revealing flashes of the brilliant detective he used to be, even though his everyday demeanor appears jaded, weary, and past his prime. Right now, he’s on the floor, struggling with joint pain.