Through Sonoko's contacts, she invites Ran and Conan to attend the pre-opening of a chocolate restaurant managed by the famous chocolatier Yukihiko Tsujimoto. During the presentation, a fire ignites and Tsujimoto burns to death. After Conan investigates, he uses Sonoko to reveal the fire was caused by using a makeshift lithium–air battery; Salt water and the aluminum cups created static electricity which ignited the steel wool and alcoholic vapors.