It's kinda weird. This episode had a lot of decent ideas, but aside from Koyomi's backstory, I didn't think that any of them were executed as well as they should have been. The 'moral' felt really tacked on in an "Oh, you're giving me a new point of view. It's time to radically change everything I've been thinking!" kinda way.
They had an interesting change of pace with their victim of the week-- who actually wanted the MOTW to succeed-- but nothing ever really came of it. As funky as it is to say, after I praised them last week for putting the victim in the background, I'd almost like to have a third episode of this 'arc' to deal more with the victim and explore that core idea some more. I think they bit off a bit more than they could chew overall.
What I found interesting was that the Ghouls were summoned from some kind of rocks. It's interesting to note that when you consider that all of Haruto's spells are contained inside of a ring's gem. From an overall standpoint, it almost looks like there's some kind of special ore that releases spells or somesuch and the user just puts power into it. I'd like them to dabble a bit more with that idea and explain just how it works.
Makes for easy scenes. Takaiwa do the normal action. Insert CGI copies of said action.
Kinda.
The thing that you need to realize about CG, even simple green screening, is that it's not a simple copy/paste job. CG is edited in post-production, so any scene you shoot involving CG has to be mapped out moreso than most and timed rather well because the live-action parts have to correspond with the CG parts.
Take that scene where Medusa snake-hairs Koyomi, for example. The CG artist has to make a skeletal frame for every one of those individual snakes, make a 'skin' (which is what we see in the end) of those snakes and put it over the skeleton, map out every single twitch and motion of said snakes, and synchronize the animation so that when Shunpei tumbles over backwards, the snakes are close, and when Koyomi goes ramrod-straight they're wrapped around her.
Then he has to export the entire sequence to a new video file so that it can be edited into the show. Depending on the system that he's running, rendering can take anywhere from one hour to several. I've worked with departments where we had to leave our system running overnight just to process a one-minute animation. Factor in the additional time for tweaking or just for the computer to crunch the numbers that you're giving it and it becomes very time consuming very fast.
That process gets more and more complicated the more snakes are on-screen and the more motion that is attached to them. It's a bit more involved than typing in 'go from Point A to Point B'.
For the Copy scene, note that when the camera's pulled back, shooting straight-on and there's distance between the copies, they green screen more Takaiwa's on screen as needed. It's simpler than straight up CG, but still more involved than your standard post-production edit job since they have to bring in the magic circle, animate the magic circle, and slide-fade more Copies in as need be.
When the camera tightens up and films from the side, then green screening is no longer an option because of the overlap among the Copies. They have to go to CG. They took some shortcuts with that scene, but they still had to import and set the animation and synchronize it. Now factor in the importing and animating of the magic circle and the disappearing arms. You're piling more work onto the scene and requiring more time for the animators to do their thing. And more time to render.
My overall point here is that we take CG for granted because it's rather prevalent in today's media, but it's by no means quick or as simple as snapping your fingers. It can become a time and money black hole very, very easily-- especially if you mess up the animation somewhere along the way.