Vengeful murderer Kikue Tanaka
Kikue Tanaka (Hiroko Fukuda) is the villainess of "Magic Lover's Murder Case", the 3-part Season 5 finale of Case Closed (airdates January 25, February 1, and February 8, 1999). She was a member of an online club of magic fans, with her chatroom username being "The Fake Child".
Kikue's backstory revealed that she was also the granddaughter of a famed magician "Halloweif", who died while performing a trick that he was goaded into performing by the members of the club. After her grandfather's demise, Kikue found out about the club he was in after finding a chat log he'd kept of them. After seeing Tsutomu Nishiyama and Toshiya Hamano (two fellow members) callously mocking Halloweif's death in the chat, Kikue began plotting revenge against the magic fan club.
Kikue began by joining the chat group herself, both under her aforementioned username as well as through another account with the name "Dark Master", using the latter account to send vicious and chilling accusations against the club members. Kikue then organized a club meeting at a snow lodge before beating Nishiyama to death in his home, writing "Dark Master" on his computer to show she intended to target the rest of the club. At the meeting (which was also attended by club member Sonoko Suzuki, her friend Ran Mouri, and Conan Edogawa), Kikue convinced Toshiya to use a card trick to determine the chores of the club members since their leader hadn't arrived, having arranged the cards to give Toshiya the role of coming up with game ideas.
Once he was alone in his room, the evil Kikue strangled Toshiya to death and used a crossbow to shoot arrows with durable strings attached to them into the trees surrounding the lodge, using them to position Toshiya's body out into the empty snow-covered field to set the murder up as an "impossible crime". Kikue later set the bridge leading off the island ablaze in order to retrieve the arrows before the police could and used another crossbow trick to make it appear someone outside the lodge was firing arrows at them, doing so to deflect suspicions.
Conan, however, was able to deduce Kikue's guilt and impersonated Sonoko to expose her. Kikue initially denied everything and poked holes in "Sonoko's" deductions, but she was ultimately revealed as the killer when Conan revealed that she had one of her arrows hidden in her boot, Conan having called everyone out of the lodge so Kikue wouldn't have time to hide it. Defeated, Kikue pulled out the arrow and confessed to being "Dark Master" and murdering Nishiyama and Toshiya, stating that while she didn't hold the group responsible for her grandfather's death, she was driven to take revenge after seeing how her victims had mocked her late grandfather. Kikue was presumably arrested offscreen.