Michiko Oosawa (Ryoka Yuzuki) was a villainess from "Venus' Kiss", episode 7.07 of Case Closed (airdate November 22, 1999). She was an actress who was the star performer of an aquarium performance, portraying the play's star character "Venus". Michiko invited detective Kogoro Mouri to her performance, having become a fan of his work.
It was during her performance, however, that Michiko was found dead, having seemingly drowned to death after becoming trapped inside the shell her character was supposed to swim out of. Her death was originally believed to be an accident, but Conan Edogawa ultimately deduced that Michiko had been murdered by Yasuyuki Murakawa, the head of the performance staff.
After being confronted by Conan, who was impersonating Kogoro, Yasuyuki confessed to killing Michiko and went on to reveal his motivation, this serving as Michiko's posthumous villainous reveal. Two years prior, Michiko had committed a hit-and-run accident, one that claimed the lives of Yasuyuki's wife and child. One day, at work, Yasuyuki overhead Michiko talking with her father, and it was during the conversation that the evil Michiko laughed at the fact that Yasuyuki didn't realize who she was. Angered by Michiko's lack of remorse for her actions, Yasuyuki attacked Michiko before her performance, knocking her out and placing her in the water tank she was to emerge from, where the villainess eventually drowned to death.