Yoko Araide (Kumiko Hironaka) is the villainess of "The Blind Spot in the Darkness", episodes 7.08 and 7.09 of Case Closed (airdates November 29 and December 6, 1999). She was the second wife of Yoshiteru Araide and the stepmother to his son, Tomoaki.
Yoko's backstory revealed that she had been best friends with Chiaki Araide, Yoshiteru's first wife who died in a drunk driving accident. Yoko, having learned that Yoshiteru was an unfaithful man to Chiaki, believed that he was responsible for her death and vowed to get revenge for her.
Yoko went about executing her revenge during a dinner her family was having, with Yoshiteru inviting detective Kogoro Mouri, his daughter Ran, and Conan Edogawa to join them. While Yoshiteru was taking a bath before dinner, Yoko set up the home's electric system to have a short circuit. During that time, the evil Yoko went into the bathroom and placed Yoshiteru's electric razor into the bath water, resulting in her husband being fatally electrocuted when Hikaru Yasumoto (the Araides' maid) caused a second short circuit when she attempted to turn the power back on.
Yoshiteru's death was initially deemed an accident, but Conan was able to uncover clues leading him to realize Yoko's elaborate scheme. While impersonating Kogoro, Conan managed to show how Yoko had committed the murder of her husband, exposing her as the killer. Cornered by the evidence, Yoko confessed to orchestrating her husband's murder, revealing her wrath at Yoshiteru for (in her mind) driving Chiaki to her death with his adulterous actions. After her confession, Yoko submitted herself to arrest and agreed to falsely claim to have used the electric clock to electrocute Yoshiteru, as to not hurt Hikaru with the revelation that she unwittingly caused her employer's death.