What an epic way to end the chapter!
I was expecting the wall to crack because he could not control his magic, but instead of that tiny flying thing, I thought the wall breaking apart. And then, lo and behold, turn out the wall breaking apart because of a whole herd of dragons shows up! Absolutely mind-blowing!
Been a while since the last update. For some reason I was under the impression that he was sent to another world, but I guess not since his sister is here?
Some kind of alternative reality like Burn the Witch or Bleach probably. Another possibility is just another pocket dimension like storage magic.