Princess Principal's chief issue lies in the characters, as there is absolutely no character development throughout its twelve episode run time. Each character gets at least one background one shot story to give you an idea of how they joined the team or got to where they are, but they are essentially never relevant to the plot (Beatrice's in particular is barely even seen, let alone matters) and do not end up driving much of anything or even giving us much more of a sense of the characters. Chise's is the closest and it is still mostly tepid, although it at least has a full and complete self contained story...and then she got another generic focus episode that served solely to show off characters you don't care about who will never appear again and stuff you already knew!
I like the idea of how the background stories were structured, starting us with the team on a mission already and then slowly showing us how they got here while mixing in more present episodes, but the fact that these backstory episodes are totally lacking in substance just kills the concept in the crib. The princess was just about the only character I thought was interesting, although she is a pretty unrealistic character, because her episodes were executed somewhat different than normal via the latter episodes. It was more tied into the overall story than the one shots and offered more character insight in the process. Can't go into too much detail here since it'd be a spoiler, although you will most likely figure out what happened by the end of the second episode.
The overall series plot is only barely existent, with the series largely consisting of one shots and an ending 2-parter. The 2-parter would have definitely benefited from some foreshadowing. It wouldn't be hard to tie more of the one shots in to it when almost none do. For example the episode about smuggling nerve gas through could have instead been about smuggling through some materials which are used in the final episode. You know, basic stuff. Granted, the finale isn't good either and has one of the goofier villain exits I've seen as they escape the plot after suffering a minor setback.
The one shots aren't that great either and suffer from an issue that the first episode already kind of tries to spell out (albeit trying to spin it as a good thing) and which is obvious from just watching 1-2 episodes more: Nearly every episode of this show is going to have some kind of plot twist shoehorned into it. Once the viewer understands this, almost every episode becomes painfully predictable as despite the show trying to sell you on "twists" it never really tries to be inventive, do anything new or even execute what it does in a manner that advances the characters. I wouldn't mind the lack of inventiveness if not for the last point, as the execution is pretty much boring and expected without using it to enhance the show. Episode 6 was the height of this to me: Unless you either have somehow not gotten what this show is about at that point or have never seen this style of plot before, you will figure out exactly what is going to happen at least halfway through the episode if not sooner. It was extremely disappointing and going for a different ending which could further Dorothy's character would have made it much more engaging.
This is compounded by the fact that this is one of those series where all of the characters are unbelievably competent and thus makes it difficult to feel tension in scenes. Most of the time, their plots don't even go all that wrong and thus there is not a lot of challenge felt: There are a pair of recurring antagonists so forgettable I don't even remember their names and they always come off as less competent than the show presents them due to repeatedly losing and being foiled in frequently easy ways. When the show tries to end on a stinger of them preparing for future conflicts, it is difficult to take them seriously due to this. For an idea of how unbelievably competent some characters are, the backstory of one says that they cannot read or write, but that they then learned NINE LANGAUGES...without anyone helping them. While also learning about 10 other listed things! It completely destroys any willing suspension of disbelief when it is so outrageous, especially since the setting otherwise plays out as somewhat realistic but with some ill defined magitech.
If there's one thing Princess Principal did solidly enough, it was the art and sound. All of the girls are reasonably cute, the background art is at times fairly pretty, it has a very victorian feel to it mixed with some industrial stuff, so if nothing else that works. The CGI on the other hand is pretty hit or miss. Stuff like the car is usually fine if sometimes a bit jarring, but the last car chase scene for example looks pretty bad (the CGI train made me laugh for a bit, which is not what you want from your dramatic heart pounding scene usually!). The soundtrack was a bit more forgettable, but there were some decent background tracks and the OP and ED are solid. Overall, this was one area where Princess Principal largely felt reasonable.
I was honestly somewhat surprised by how much I disliked this series by the end of it. It started off fairly standard and I thought it would be some general 4-6 star anime fodder. Instead the complete lack of character progression, lackluster one shot plots, lack of an overarching story and absence of tension completely stifled the show for me and left it a pointless slog. I would recommend avoiding this anime unless you are a hardcore spy fan (although you might even be more annoyed by me at how lackluster it is if you're hardcore into the genre), have some character design or part of the concept really jump out or simply want to watch as much anime as possible.
