Chocolate's Hot Trap

Conan, Ran, and Sonoko are invited to the opening ceremony of a chocolate shop that is supported by the Suzuki Group. They meet a woman named Mayuko Sakura, the shop producer. Next they meet a man named Yukihiko Tsujimoto, the chocolatier and he's Mayuko's fiancé. During Tsujimoto's show, the fire breaks out in the shop, killing Tsujimoto. Was this a terrible accident or a planned murder?