This OVA takes place ten years in the future and chronicles the possible events if Conan Edogawa and Ai Haibara do not take the antidote to APTX 4869 and grow up alongside their friends Genta, Mitsuhiko, and Ayumi, while still maintaining their detective endeavors.

Professor Agasa is kidnapped and the Detective Boys must use clues found at his house and in various parts of the city in order to find him.

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's 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.

Once again, Kaitou Kid has a target in mind: the Crystal Mother, Europe's largest topaz owned by Queen Selizabeth of the Principality of Ingram. He intends to steal this jewel while the Queen is stuck on a train from Tokyo to Osaka. However, Kid's abilities are put to the test, as the Queen has already concealed the gem somewhere aboard the train. Conan Edogawa, who is among train's passengers, suspects an attack from the phantom thief and begins investigating on his own, while Inspector Ginzou Nakamori is ready for a new confrontation against the elusive jewelry robber.