WARNING: Some fairly minimal spoilers ahead.
Created by Matsuri Akino and released originally in 1995, ancient as far as manga goes these days. It's long been one of my favorite series, despite the fact that I've never been fond of the art style. But I like supernatural mystery's. Along with the greater mystery of Count D, there are individual puzzles that you get to see through the eyes of Detective Leon Orcot.
Usually Leon does not look so suave.
Leon is a bit of a problem character for me, as much as he is necessary for the story to unfold, sometimes his choices baffle me. He leaves his kid brother in the care of someone he believes to be a felon, allows said felon access to his home. It's crazy, and folks in the story mention that he's a good detective, but there's not really anything you get to see that proves it. Don't get me wrong, I like him, he's a good person, and the only person who ever seems to ruffle D's feathers (and D deals with mob bosses and puppy kickers).
Anyway, if you're not familiar with the series, it revolves around Count D's Petshop in Chinatown, a business he's taken over from his grandfather the original Count D. Inside is every kind of pet you can imagine from birds and fish to kirin and dragons. And to a select few the pet's seem almost human. D's motives are all over the place, sometimes he aims to punish an owner, sometimes to help, he's not a character you can box in despite what the ending of the series tells you.
It's really a beautiful, and horrible series, if you liked CLAMPS XXXHolic I suspect you'll fall head over heels for this one as well.