Opera House Murder Case: File 1 - S1-E21
Other mistake: Kindaichi and Miyuki are chatting with the lead actor who is sipping a Coke. There's a fierce argument onstage between the actresses; somehow the actor, in full stage garb, calmly shows up onstage to catch the end of the argument way before the other two kids get in the room running. (00:10:00)
