Yukiko Kudo, born Fujimine in Tosa Province (modern Kochi Prefecture, Shikoku), derived her maiden name from Lupin III's Fujiko Mine and actress Yukiko Nikaido. During Teitan High School, she rivaled childhood friend Eri Kisaki for "Miss Teitan," resulting in a tie due to Kogoro Mouri's error. Achieving teenage fame as an actress, her portrayal of Sakamoto Ryoma's sister Otome brought international acclaim and prestigious Japanese awards by age 19. While studying disguise under magician Toichi Kuroba, she befriended actress Sharon Vineyard. This close bond lasted until Yukiko discovered Sharon's secret life as Vermouth of the Black Organization following her faked death. At 20, Yukiko abruptly departed acting after marrying mystery novelist Yusaku Kudo, though accounts vary on their meeting and marriage timing. Post-retirement, she earned the "Night Baroness" moniker after solving a case on television using Yusaku's literary references. Yukiko maintains a youthful, exuberant personality, displaying playful, attention-seeking behavior. She reacts strongly to being called "oba-san," insisting on "onee-san." She exhibits occasional jealousy over Yusaku, notably after an incident where he returned home drunk with lipstick. Her loyalty drives her to travel internationally to aid friends and family. She takes significant pride in her acting legacy and disguise skills, which allow her to convincingly impersonate others, even fooling close acquaintances. Her driving is notoriously reckless, disregarding traffic regulations. Her skills include exceptional mastery of disguise learned from Toichi Kuroba, enabling undetected impersonations like Fumiyo Edogawa or Yusaku Kudo. She possesses sharp deductive abilities, considered inferior to her husband and son. Her driving is dangerously erratic; she holds or held a California driver's license with the ID "471108628," a number inconsistent with standard California formats. Yukiko plays key roles in significant events. She first appeared disguised as Fumiyo Edogawa, claiming to be Conan's mother, part of a test with Yusaku to evaluate Shinichi's skills and convince him to leave Japan for safety; he declined to stay near Ran and pursue the Black Organization. Later, after a marital disagreement, she secretly returned to Japan and helped Conan craft an elaborate fictional family tree to dispel Ran's suspicions. During the Bell Train arc, she adopted the identity of a woman visiting Subaru Okiya, collaborating with Conan to thwart Bourbon and Vermouth. She removed Haibara from danger, confronted Vermouth to distract her from Conan's deception, and secured Vermouth's promise to cease targeting Sherry. Later, she impersonated Yusaku at an awards ceremony and assisted Akai Shuichi in reapplying his Subaru Okiya disguise, nearly revealing Conan's identity as Shinichi to FBI agents. Her relationships include a close marriage to Yusaku Kudo, with whom she has one son, Shinichi Kudo. She affectionately calls Shinichi "Shin-chan," enjoys teasing him, and worries deeply about his safety. She considers Ran Mouri a perfect match for Shinichi and a potential future daughter-in-law. Her meaningful friendship with Sharon Vineyard ended upon learning Sharon's dual identity as Vermouth, deeply troubling Yukiko. She maintains a lifelong friendship with Eri Kisaki despite their high school rivalry. Trained by Toichi Kuroba, she later interacted with his son, Kaito Kuroba (Kaitou Kid), who calls her "old lady." She shows protective concern for Ai Haibara, interpreting Haibara's expressions toward Conan as romantic interest and risking herself to save Haibara from the Black Organization.