Detective Kogoro Mori, his daughter, Conan, and the Junior Detective League were invited to an amusement park in Yokohama, Kanagawa Prefecture. However, the trip took a sinister turn when they fell into a trap set by the client. Each individual was given a wristband before being allowed to explore the park, except for Kogoro and Conan, who were shown a video of Kogoro's acquaintance, Ryu, being held captive. Conan noticed that the client was wearing the same wristband, which suddenly exploded. The client then revealed that the wristbands they were wearing had been rigged with bombs. Additionally, the wristbands of those exploring the park were programmed to detonate if they left its premises. Despite Conan's attempt to warn Haibara and the others, it was already too late. The client then presented a grim ultimatum: solve the riddles he posed within 12 hours or face fatal consequences. Reporting the incident to authorities was strictly prohibited.