Ayumi Yoshida, a first-grade student at Teitan Elementary, is a founding member of the Detective Boys and lives with her parents in a high-end condominium. Initially the group's sole female member until Ai Haibara joined, Ayumi possesses a naive and innocent personality marked by a cheerful spirit that boosts group morale. She gradually develops courage during investigations. She persuaded Conan Edogawa to join her, Genta Kojima, and Mitsuhiko Tsuburaya in exploring a haunted mansion, leading to solving a homicide and forming the Detective Boys. After Conan rescued the group from mafia members during an early case involving stolen Italian gold coins, Ayumi developed a serious crush on him, causing Conan discomfort and sparking jealousy in Mitsuhiko and Genta, who both harbor feelings for her. Ayumi sometimes misinterprets Conan's protective behavior toward Haibara as romantic interest, though she ultimately forms a close friendship with Haibara, who allows Ayumi to call her "Ai-chan." In investigations, Ayumi contributes through simple yet astute observations. She deciphered a code from a Momotaro container by connecting it to statue directions at the Oohara Art Museum and notices subtle details like inconsistencies in a suspect’s appearance. Her problem-solving aids case resolutions, such as the collective solution to a mystery in episode 259. In the OVA "A Challenge from Agasa! Agasa vs. Conan and the Detective Boys," Ayumi participates with the group in solving the mystery of Professor Agasa's coded kidnapping challenge, leading to locating a kidnapped girl and apprehending suspects Osamu Yoda and Miki Ogura. Ayumi maintains respectful relationships with adults, addressing Hiroshi Agasa as "Professor" and using formal titles for officers like Wataru Takagi and Miwako Sato. She uses familial honorifics for older characters, such as "Ran-onēsan" for Ran Mouri and "Shinichi-oniisan" for Shinichi Kudo, reflecting her polite and observant nature.