Invaders of the Rokujouma!? Volume 15

Deciding they need a bit of a break, Koutarou takes the girls out for a day of beetle hunting. An unexpected reunion, however, leads Kiriha to realize there's more than just beetles in the mountains outside of Kisshouharukaze City. It seems the radical faction has been working in the shadows all this time, and they've already established a foothold on the surface. But a factory? Magicians? Automated weapons? It sounds like they're preparing for something big, but this is only the beginning.