The culprit is Heihachi Mikami. Ryoji Amatsuchi reveals he prevented everyone from leaving his inn in order to know who had murdered his friend Asao Kono. He eventually plugs the inn's phone cable again in order to call an ambulance, since Ai is "suffering from a violent stomach ache".
The police arrive later on, and Conan hears the sound of Yamamura's dialling a number on his phone's keypad, whose music reminds him strongly of Vermouth's message to the boss of the Organisation. Yamamura tells Conan he's phoning his grandmother in Tottori.
Conan reveals the culprit to be Kyosuke Haga. As Kyosuke is taken away, he is a composer who has the perfect pitch so Conan asks him the tune of a song from the cellphone numbers and finds out the Boss of the Black Organization's number is the song "Nanatsu no Ko".
