Chu You emerged from the underground chamber alone this time. Although it was an underground chamber and smaller in space, it had become fully automated, with facilities such as wireless television, wireless computer, washroom, refrigerator, and so on—everything necessary for basic human living was present.
The underground chamber was entirely under Xiao Qiao's domain. Even though Miyashita Nanoha was an evolver, her evolved special ability wasn't destructive, so there was no need to worry about her escaping.
Keeping Miyashita Nanoha in the underground chamber was at Xiao Qiao's request, to train and transform Nanoha into someone useful for Xiao Qiao!
Chu You vaguely felt that in this world, his alliance with Xiao Qiao might not be unique. It was possible that in hidden places around the world, other evolved beings had been chosen by her, forming alliances like the one between himself and Xiao Qiao.