Case Closed: Conan and Kid and Crystal Mother(2004)

Meitantei Conan: Conan to Kid to Crystal Mother

Kaito and Aoko are traveling on a train along with Aoko`s father, Inspector Nakamori, in attempts to help stop Kaitou KID from stealing a precious gem known as Crystal Mother. Little do Aoko and Inspector Nakamori know that Kaito is Kaitou KID and he will do whatever it takes to retrieve the gem. Unfortunately for Kaito, he is also being followed by Conan and a little boy named Philip who will do anything to stop him.

(Source: Anime News Network)