Overall, this was a good read, but it seemed a little disjointed.
The final part of the Visitors Arc, plus a short story about Mayumi. The plot seemed to be rolling along pretty well in the first two parts of this arc, but when it came to wrapping everything up it seemed like I was reading somewhat disconnected fragments rather than a cohesive whole. It was not unenjoyable, but it did feel disjointed and I wasn't clear on the logic of some of it. Too many cogs, I think. There were so many disparate groups involved, so many political angles and machinations, that it was hard to keep track. Especially when some of them appeared to pop up out of nowhere just to complicate things. I got the vague impression that the author wanted this story done with and cut a few corners, but it doesn't detract hugely from the story.
The short story at the end gives us a view of Mayumi Saegusa's home life and Japan's only acknowledged strategic magician. It's main purpose appears to be to introduce Mayumi's younger twin sisters who are going to turn up at First High in the next book. The story is really just filler.
Overall, not bad, could be better.