The one-shot (chapter zero in the scans) is a prototype of the story, and is one of the better one-shots I've ever read. It's funny, creative, and has a great ending. I highly recommend it.
The first two volumes are a mediocre seinen romance, focusing on the rocky relationship between two classmates who are course and violent in real-life, but are both caring and romantic online.
The last three volumes focus on their part-time job, as investigators for an online social networking site. It reads like a pretty-good, episodic mystery manga. It's never especially dark, some of the incidents are pretty funny, and most are resolved satisfactorily.
The problem is that the transition between the two stories is not handled especially well. The first two volumes read like a fairly melodramatic seinen: the guy is kind of an idiot and the drama is a bit forced, but the characters are really interesting. Then, suddenly, the romantic parts are over (except for some off-hand remarks here and there, and one or two chapters that feel horribly out of place) in favor of a pretty good mystery manga. And, ultimately, the resolution to both is extremely rushed; you do get a happy ending, but it comes with very little setup and is pretty unsatisfying.
I will say that the artwork is consistently very good. The small details (particularly on some of the jewelry later on) are beautiful, and the character models are consistent and clear.
Mel Kano is a different and interesting manga. But ultimately, I'm not sure who wants to read it (outside of the one-shot, which again, is excellent). There are much better seinen romances, and much better detective stories. Still, it's certainly not bad, and I doubt that you will regret reading it either.
