Hiroshi Agasa lives next door to Shinichi Kudo in Beika City, having attended Teitan Elementary School and Okuho Middle School in his youth. His family background features deceased parents and relatives: gadget-loving great-uncle Kurisuke Agasa, who died fifty years ago, and great-aunt Teiko Agasa, who passed away more recently. An unnamed cousin and that cousin’s granddaughter also form part of his extended family. During elementary school, he forged a significant bond with Fusae Kinoshita, later the fashion designer Fusae Campbell. Their childhood promise to reunite every decade culminated years later, suggesting a rekindled relationship. Agasa earned a doctorate through Toto University’s engineering program. As a pivotal confidant and inventor, Agasa became the first person to learn Shinichi Kudo’s true identity after the APTX 4869 poison transformed him into a child. He devised the alias "Conan Edogawa," provided gadgets like the voice-changing bowtie and turbo-engine skateboard for covert detective work, and enrolled Conan at Teitan Elementary School, catalyzing the Detective Boys' formation. Later, he sheltered escapee Shiho Miyano from the Black Organization, renaming her Ai Haibara and integrating her into the group. Agasa maintains Conan’s cover by posing as a detective during investigations, lip-syncing Conan’s deductions. He informed Shinichi’s parents, Yusaku and Yukiko Kudo, about their son’s condition and collaborates with allies like Subaru Okiya against the Black Organization. Aged 52-53, Agasa appears older than his years, sporting a bald head, silver hair, a thick mustache, and a slightly overweight frame. He typically wears round glasses and a lab coat. His yellow Volkswagen Beetle frequently suffers mechanical issues like flat tires. Jovial, intelligent, and paternally warm, he enjoys deep community trust, aiding his explanation of Conan and Haibara as "children of friends." He chaperones the Detective Boys on outings—many inadvertently involving criminal cases—while Haibara monitors his diet and health, reflecting their familial bond. Agasa excels at winning food-related prizes but achieves inconsistent success with inventions: some gadgets prove essential; others malfunction or cause property damage. His fondness for pasta and tomato juice is well-documented. The name "Agasa" derives from Agatha Christie, with "Hiroshi" serving as a pun on "hakase" (professor). Speculation once positioned him as the Black Organization’s leader due to his scientific expertise and early narrative prominence, but this was explicitly refuted. He remains integral through ongoing support for Conan and Haibara, gadget development, and mentorship of the Detective Boys.