Conan and Sonoko arrive at a dojo in Osaka where Kyogoku is training. Takami, the master of the dojo, once provided Kyogoku with a great deal of help with his karate training. While Conan and Sonoko watch the children practice, Kajiyoshi shows up to get Takami's signature on their agreement. Operating the dojo has become difficult to the point that Takami has taken out a loan, and he is considering selling the dojo. Later, an important black belt is stolen from the dojo's display case. When Kyogoku is suspected of stealing the belt, he challenges Takami to a fight. If he wins, the dojo will remain open, and if Takami wins, he'll return the belt...

The body of neighborhood nuisance Amagi is found in the park of a high class neighborhood. He was murdered around 9 PM the previous night. The body was stabbed numerous times by an awl-like weapon. Next to the body is the bloodstained medical examination card of neighborhood association president Bando. The police head to Bando's home to question him... but Bando has been poisoned with a combination of liquor and pesticides, and near the body is a bloodstained awl. Detectives Takagi and Chiba believe that after stabbing Amagi, Bando chose to end his own life, but...