As remarkable as Kara no Kyoukai is, however, it's still far from perfect. There are definitely things that not even stratospheric production values and stunning choreography can make up for in the long run. Keep in mind that the point of U2 is to dig for flaws and get a sense of what’s running through the minds of those who are maybe not so keen on dubbing the series an unassailable masterpiece.
The mere fact that I adore Kara no Kyoukai and could gush about it ad infinitum is, truthfully, quite surprising seeing as I don't think very highly of the Nasuverse in general. I've read the Tsuikhime visual novel, seen the most-undeniably non-existent anime adaptation, and slept through two viewings of Fate/stay night. Honestly, I still don't get what all the fuss is about.
Shiki does not approve of being trapped in such an undignified universe.
A good analogue for the works of Kinoko Nasu, Kara no Kyoukai included, would be the Metal Gear Solid video game (movie) franchise. What begins as a delightfully refreshing spin on a stale concept quickly falls victim to overambition, or, as I like to call it, indulgent inertia.
Yahtzee once said that Metal Gear Solid was a series in dire need of an editor, preferably one armed with waders and pruning shears, and the exact same could be said about the Nasuverse. There is simply far too much tedious terminology and referential material, most of which has zero relevance to the immediate plot. And, of course, any terms that do turn out to be relevant are nonchalantly strewn about as if the audience had already pored over the entire Type Moon Wiki. It's like in Final Fantasy XIII, where you're never told what a l'Cie is, but the word is used about 20 times in the first half-hour alone. I'm sure it doesn't take a Literature major to realize that this is not good storytelling.
As much as I disapprove of the Codex in Mass Effect, I can at least appreciate the fact that it’s a coherent, professional compendium, whereas the background information found in the Nasuverse has the quality assurance of the majority of fanfics found on DeviantArt. So much of what has spewed forth from Nasu's head is clutter; it's jumbled, pretentious, and juvenily indulgent and I’m only talking about the stuff that's actually pertinent to the story because sifting through everything else is like filing through a trough of Dead Apostle entrails.
Bringing it back to Kara no Kyoukai, yes, the series is also tainted by its proximity to said bucket of slop. Here are some pressing questions that I can think of right on the spot: Just what the hell is a bounded field? What exactly is the “origin” that Shiki has a connection to and that Araya is seeking to obtain? For that matter, what's the deal with this unique “origin” that everyone possesses?
It's true that “show, don't tell” is a hallmark of good storytelling and yes, viewers are not morons. But they're also not geniuses. When “less is more” is taken to such an extreme degree, it forces us to fill in answer E on the SAT Math scantron, i.e. “Not enough information.” I do appreciate the fact that Kara no Kyoukai is devoid of Nasu's trademark clutter, but the clean-up crew did far too good of a job when they decided to sever certain pivotal plot strands altogether.
Like Metal Gear Solid (2 specifically), Kara no Kyoukai leans not only on the cool factor as a crutch, but mind-numbing perplexity as well. Granted, there is a lot of appeal in the unknown and a plot shrouded in mystery is inherently engrossing. But there comes a point where things suddenly turn opaque and impenetrable. Whereas the gimmick in the fifth movie successfully milked its mystique without going overboard, the overall plot of Kara no Kyoukai is guilty of having long crossed said threshold.
More disjointed questions: What was the point of the sixth movie in general? What's the story behind the Fujou, Asakami, and Ryougi clans? What are the basic rules governing magic in this universe? Again, the cool factor and superb presentation are powerful tools, but one only has so many free passes to hand out. Some may call the narrative undernourishment a result of the series being economical, but shortchanging the storyline to such an excessive degree is not to be applauded.
Naturally, the Nasuverse is not done smearing its blemished pedigree all over Kara no Kyoukai's otherwise streak-free surface. One trend that the Nasuverse seems dead-set on continuing is the creation of a cast that is stillborn with the exception of at most two stand-outs. I would say Saber and Rin Tohsaka from Fate/stay night, Arcueid Brunestud from Tsukihime and, of course, Shiki Ryougi from Kara no Kyoukai. Everyone else is simply flaccid and lifeless; not only are they bland upfront, but they never evolve beyond their neanderthalic archetypes.
It's pretty sad when the minor one-shot characters far outshine the central cast as the likes of Fujino Asagami and Tomoe Enjou put Touko Aozaki and Mikiya Kokutou to shame. Mikiya gets better during the finale, but remains firmly entrenched in Dogged Nice Guy territory. So nice that it hurts is a pretty good evaluation. Touko is cool in that aloof big sister sort of way but receives appallingly little development for her importance to the plot. Even Souren Araya, who, before his official introduction, seemed like he would make a compelling villain, ultimately ends up as nothing more than a misguided, militant crusader.
I wouldn't say any of these characters are outright bad, but without Shiki, this majestic vessel would find itself speeding towards the bottom of the sea. Everyone is an anthropomorphic personification of some crucial plot element; they exist only to underpin the plot and the aforementioned select, spotlight character. They’re the equivalent of wood polish, which by itself is nothing more than greasy, smelly, oily slime.
Whew, that was pretty rough! To me, these are all petty grievances, especially when Kara no Kyoukai is compared to the rest of the Nasuverse. Plot pratfalls and an uninteresting supporting cast are inconsequential flecks of mold on the otherwise sublime key lime pie that is Kara no Kyoukai whereas Fate/say night and Tsukihime are pastries completely coated in fuzzy, teal-white patches.