The Blind Spot in the Karaoke Box (Part 2) Meitantei Conan : Season 17 Episode 18

Conan knocks Sonoko out with a tranquilizer and solves the case. Afterwards, Eisuke reveals he wants to ask Shinichi Kudo for permission to admit his love to Ran and take her to America. Conan tells him he can not and Eisuke confesses that he had found out at the very beginning that Conan is indeed Shinichi.