The guard captain strikes me as someone just wholly unprepared to deal with a small child. He's got two modes: deference to Alicia and her father, and "see threat -> deal with threat", and it doesn't matter who or what that perceived threat is.
Because the moment he gets called out, and the moment he sees what Ferris can do, his whole demeanor shifts away from aggressive. I
hope this means he'll become a staunch ally of Ferris' and of Alicia's, and not be a (substantial) thorn in their side as the story goes on. Something like a bumbling fool who doesn't actually mean malice or harm, but is just 'always at 100' with whatever he's dealing with.
But yeah. This series just makes me heart hurt, seeing Alicia react to every thing she learns about Ferris' life & situation. I agree with
@Miserys_End and that she doesn't need to be bubble-wrapped, but she
absolutely needs love and care and affection and a solid education, to both learn how to operate in the world she's found herself in, but also to discern good from bad and right from wrong (at least to the most benevolent moralistic standard possible).
Too bad I'm willing to bet all my marbles-and-then-some that her Summons are
not going to play by that rule book. But I
do hope that they take any sort of fealty to Ferris very seriously, and while they may wish to destroy the world whenever they're summoned, they'll actually listen to her every time, immediately, and as Ferris learns more about what she should do in life, she'll develop a relationship with them and learn to control them better and better.
Loving this series though, and I cannot wait to see what's next. Thanks for doing what you do and for picking this up and caring for it so.