There is an episode in Conan, a famous detective: Haiyuan Ai was arrested and left a message (it seems to be "black"). Conan was rescued after cracking.

Hello, I'm Conan. I am a member of the team. Glad to answer your question _

This story appeared in volume 34 of the comic book special? File.11-12 The Dark Hunter (er ... title and m? 13 ...).

The resources of online comic articles are extremely scarce, and it is a pity that we can't find online resources. But I have a copy at hand and took some photos in a hurry. Please forgive me if the effect is not good.

The final discovery of the story was just a false alarm. The words left by Ashala are not "black", and the so-called "men in black" is just an ordinary person wearing black (to be honest, I have a feeling of being cheated ...)

I hope I can help you?