If you loved Detective Conan: The Darkest Nightmare, try Detective Conan: Black Iron Submarine
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

Detective Conan: The Darkest Nightmare
→
Try this next

Detective Conan: Black Iron Submarine
What they share
Theysit in Action / Animation / Crime / Mystery territory. If that's the register that drew you to Detective Conan: The Darkest Nightmare, the second film will land in a comparable space — through a different lens.
What Detective Conan: Black Iron Submarine is
Tokyo, summer. A distant buoy. Interpol's data hub goes live in the Pacific, but a shadowy group snatches a key engineer, and Conan smells foul play. Classic locked-room anime hijinks for the whole family.