It took so many episodes to set this up, holy cripes; I haven't seen stall tactics this bad since DBZ.
By the end of episode 17, we're in exactly the same place we were at the end of episode 16 (except the teachers are learning what's going on and Iruma finally arrived at the room). I was actually, for the first time since watching this anime, skipping through the more "boring" parts to try and get to what the protagonists were doing.
It's fine to show the students panicking and-or making their way through the maze, but it felt like that became the focus instead of more on how they're working to fix things (and how the teachers handle it; I will admit that it's nice to see a school with competent teachers for a change).
And to think...we still need the "confrontation scene" (between Iruma and Amy), then the "tragic antagonist backstory" (Amy's past), the "eleventh hour", followed by the "heroic turn of events" (the climax where Iruma will probably unleash all the power in the ring or something like that and everyone will just be treated to a giant fireworks show), then the "conclusion".
If they keep the pacing the way they've been doing it, they'll be doing each of those things per episode (as honestly, if they took out all the silly filler from the past episodes, we could at least be up to "tragic antagonist backstory" by now) which will prolly bring us to...episode 22 or so for this arc, so that the final couple episodes can go back to being comedy (and perhaps some new resolve on goals/dreams from Iruma).
I'll be surprised if I'm wrong. Best-case scenario (less stalling), they wrap up this arc by episode 20.
Hilariously enough, it all could have possibly been avoided if Iruma had gone to that room when they were looking for Amy during the daytime. I kept wondering why he didn't go there when they were searching for him...now I know that he didn't go there because the plot said so. >.>