Conan Edogawa and his classmates are assigned to do a class report about a small business of their choice. After discarding other possible topics, the Detective Boys concludes that it is a perfect opportunity to find out more about Detective Kogorou Mouri's job.

Conan's friends refuse to settle for a simple interview, though, as they want to experience first-hand all the details of his work. Thus, they, along with a reluctant Conan and Ai Haibara, decide to tail the renowned detective for a day. However, the kids soon get involved in a grim situation when Kogorou's current case takes an unexpected and dangerous turn.