Atsuko Komiyama (Yumi Nakatani) is the villainess of "The Man Who Was Killed Four Times", episode 7.13 of Case Closed (airdate January 10, 2000). She was the wife of actor Taiji Komiyama, who was found dead in his dressing room from apparent bludgeoning.
Inspector Sango Yokomizo was forced to bring in detective Kogoro Mouri for his help in finding the culprit responsible due to the abnormal nature of the case: three of Taiji's fellow actors (Kengo Katsumata, Haruyuki Hoshino, and Yumiko Niikura) each confessed to killing Taiji by striking him with a vase during an argument. When Kogoro arrived at the theater, Atsuko immediately shouted for inspector Yokomizo to hurry with the investigation and return the things he'd taken to the police station.
Over the course of the investigation, Conan managed to deduce that, while all three of Taiji's co-actors had indeed hit Taiji with a vase, none of the three blows were what led to his demise. The true cause of Taiji's death was revealed to be from a heart attack, as Taiji was known for having heart troubles. In the episode's climax, Conan impersonated Kogoro to reveal that Atsuko was Taiji's true killer, having replaced the heart medication he kept in a necklace container with stomach medicine while he was taking a shower. While initially denying the claims, Atsuko was definitively exposed when Yokomizo received a call confirming that stomach medication was found in Taiji's autopsy. Atsuko resigned and confessed to killing Taiji, while bemoaning how she would've gotten away with her crime had Taiji's co-actors not struck him so hard. Atsuko was placed under arrest off-screen, with her motivation for killing her husband remaining unknown. However, it's possible that the motive was because of the (unwanted) attentions Taiji gave to Yumiko Niikura.