"Counter Stop" (正体不明 (カウンターストップ) Kauntā Sutoppu?, lit. "Unknown Identity") is the twenty-first episode of the Toaru Majutsu no Index anime series, and the first episode of the Kazakiri Hyouka Arc. It was first broadcast on February 26, 2009, and was directed Yanagi Shinsuke, storyboarded by Yanagisawa Tetsuya, and the script written by Nishizono Satoru.