For the first few episodes, this anime is amazing. It's certainly not better than Magic Kaito (Kaito Kid), but it has its own charm, wit, and approach to the entire Phantom Thief theme.
Then, a "plot" was introduced...and it crashed and burned. Imagine picking up a book and trying to read the entire novel with not just pages missing, but entire chapters. That's what the "plot" of this felt like.
Chizuko Mikami is an 11 year old girl living with her aunt and uncle after her parents passed away. Despite being the heiress to her family name and fortune, not all is as happy as it appears. When she is whisked away by the mysterious "Man of Twenty Faces", she is more than happy to go with him and his crew.
However, the Man's mysterious past starts to peek its head in, and sets forth a set of events Chizuko couldn't have predicted in her wildest dreams.
Man of Many Faces - (no, seriously...this guy's name was never given in the entire series), also know as "Ojisan" (uncle) to Chizuko and "Boss" to his crew. His past is a mystery, and he is both intelligent and talented.
Chizuko Mikami - aka, "Chiko", is a young girl who finds herself among thieves, and learns from them. She is petite, but learns to use that to her advantage...in addition to her natural cunning.
Ken - A character who serves as a "big brother" to Chiko, and teachers her knife throwing. He's a happy-go-lucky sort and is the first to welcome Chiko into their band of thieves.
Other characters come and go, but these are the main three. Antagonists aren't even worth mentioning because their backstories are incomplete and they honestly fail as bad guys due to having such ambiguous motives which drives their actions (sometimes, even contradicting their own MO).
Even the protagonists stagnate and don't really show much growth after a certain point, while a couple characters just seem to do a complete 180.
For an older anime, the animation is pretty good. The music mixes well to create a mood for the scenes where it's necessary, but a major falling point is that even the combination of the music and animation isn't enough to save the trainwreck of a plot.
The opening and ending themes make no sense (and the ending made me wonder if someone mixed up the anime with a different series until I saw the names in the credits) until abound mid-way through. So, of course, that means they spoil part of their own series right off the bat.
As for the OP and ED songs themselves...the OP song is nice but forgettable, and the ED song is just...uh, I think there was an ending song...
The first few episodes were absolutely amazing, and I would have loved to follow the adventures of this Phantom Thief troupe for the duration of the anime. Sadly, that gets derailed with the worst attempt at a plot/story I've ever seen.
It's certainly an insult to Edogawa Ranpo's antagonist character, that's for sure.
There are points in the plot not wrapped up (I'm going to give a quick spoiler and warning: If you're hoping that Chiko's aunt is somehow brought to justice for what she's done, don't get your hopes up).
There is zero resolution for a couple things we're introduced to, as well as poor buildup and almost no explanations for events which occur (many antagonists are just dropped into the plot; how one of them was able to use hypnosis on a sort of Esper level is still not explained). They appear, occasionally get one episode to have a poor flashback attempting to explain their motives (attempting, because it fails miserably), and then are defeated.
Even Twenty Faces' past is left so ambiguous and with such little buildup to it; there are "hints" of a talk about the war (presumably, WW2), but there actually isn't any satisfactory conclusion to it.
Even a couple of the characters whose pasts also go back into some trauma from the war are just sort of shrugged aside and given what I can only describe as a half-arsed attempt at developing them.
One character goes from being likeable to being a jerk, another I just can't like because when I think about it, he's always five seconds too late to help Chiko even though it's obvious he's been lurking around near her the entire time...it feels almost like he was truly manipulating her into being the decoy everyone starts talking about.
By the end of the show, I had no favorite characters.
The "plot", as well...my suggestion is to just turn off your brain if you're going to watch this. The writer obviously has no clue how to build a mystery as more and more holes just keep being opened up with no explanation or anything in order to fill them. All of the "hints" the viewers get are the same of "war", "the war", "the past"...literally, that's all they say.
"In the war"...
And nothing more. At the end of some of the mad scientist-esque arcs, they explain a tiny bit...but even at the very end, the "logic" of the Big Bad isn't logical. It makes zero sense, and so many of the things which happen are just facepalming moments of exasperation because they could have been prevented had Twenty Faces just acted five seconds sooner (and he obviously could have).
The show went from "Phantom Thief troupe" to a generic "mad scientist" trope; and the latter isn't even good.
So, the first few episodes are great, the middle is absolute garbage which makes no sense (though for some reason, Chiko just goes with it instead of saying "what the freak is going on?"), and the latter part of the series doesn't tie things together very well at all (there are insinuations and context clues, but it's never outright stated that certain events happened due to various characters moving around in the background, ect).
Thus, I can't give this a high rating. The only reason I watched it through was because I wanted to find out about Twenty Faces' past and hoped that since that was the overall plotline of the middle and latter half of the series, it would somehow allow all of the random crap which occurred during then to make sense.
I really wouldn't recommend this anime (past episode 5 at least...yes, that's how early it goes off the rails) unless you're bored.