I thought the preview already came out but it turned out only the synopsis.
Very likely minimal to no fighting (magic battles) scenes in this volume.
Considering the volume, it would like vol 17, but vol 17 kinda interesting because the reactions of Tatsuya's colleagues after that Yotsuba new year news. (Epilogue of vol 16)
But this volume 21 would be entirely in politics I guess because the end of volume 19 was kinda bland furthermore vol 20's story was isolated in artificial island.
Oh, the most interesting part in vol 20 was in epilogue but it was kinda disconnected with this so called "Disturbance" or no connection whatsoever.
So another boring volume? hopefully not
