If I had to give a specific complaint about this one, it's the amount of pointless explanation and recap. It's like the reader isn't expected to remember what happened on the previous page. It wastes a lot of time, and it annoys me. Huh.
Back to Okinawa for a little field trip to save a floating island, but since practically the entire gang happens to be there too, they might as well still be at school. I don't know, this felt kind of rushed. I know the series is sort of coming to an end at this point, but there seemed to be a lack of ideas.
Tatsuya is basically a god at this point. The author is having to drop in arbitrary restrictions on what he can do in order to make every plot trivial. Case in point: he's unable to see the area around someone he's placed a 'tracker' on for reasons. He always knows where Miyuki is and what's happening around her. How is that different?
The story also gives us a plot point (in the epilogue) which might be interesting in the future, and then yanks it back in the next paragraph. Unless something interesting is going to happen to change things, it read like the author just wanted to show how awesome the Yotsubas are for no reason. Wait and see, I guess.
Overall, however, this was more entertaining than some of the books preceding it. The combat scenes (of which there were several) were well done. The plot had a point. It did feel like a 'have to go do something in Okinawa before the end' along with a 'all these people are graduating, so better do something with them' sort of side-story. Also, there are no riots. But it wasn't bad.