A good teaser.
I found myself wondering about the points you adressed in the author's comments after I finished watching it, so I'm looking forward to seeing how that comes out. As for everything else, you seem to have a penchant for shots of entrails and gore, and while, in and of themselves are not neccesarily a bad things, but they tend to detract from the flow of the clip. Also, the animation on Sera seems sometimes seems to be of a different quality than the animation on everything else, making her stick out, and certain things, like the pages of the book blown by the wind, are animated too stiffly. They seem like solid plates instead of paper.
That aside, the rest of the animation is excellent and the direction impressive. I'm really looking forward to seeing what episode will look like.