(You can create your own case generic. Just make sure it has something supernatural about it.)

It was another ordinary day in the Narumi Detective Agency.

Gouto: "Hey, have you even checked the mail yet?"

Narumi: "I'm looking at it. Bill... bill... newsletter... Huh?"

Gouto: "Something of interest?"

Narumi: "Yeah, looks like we might have a new case on our hands. Wanna check it out, Raidou?"

Raidou looks up and nods. He walks over to the desk, and Narumi opens the letter with the new case information.