The Culprit is Genta's Dad (1) Meitantei Conan : Season 1 Episode 551

Genta's father is in a competition where anyone with the surname Kojima are allowed to participate. Conan and the Detective Boys attend to watch the competition after hearing Genta's father making past the preliminary rounds as one of the three finalists. When it is announced the competition is canceled, Conan notices the announcer has blood on his sleeve and investigates