@electro_neanderthal relax, man. This is clearly an abnormal situation, monsters appearing in what was previously a safe zone. Especially so for people who've been seekers for at most, a week? (more like, a few days) It's really not that unbelievable for them to be caught off guard. and yes, Elysha or Theresa probably should've been able to react, but clearly the intent of the scene was more about showing the competency of Polaris than the incompetency of MC and co. Could it have been better? Sure, but the author certainly doesn't need to "grow some brain cells".
And even at the end, MC reacts properly and takes out a monster. Even in the same chapter, your problem is addressed, so I don't get why you're being so harsh about it.
Abnormal situation or not, they weren't just caught off guard, they were shown to have the experience and competence of people who have never seen danger. That's called chataracter regression, and regressing characters to make other characters look good is objectively bad writing—especially when it would have been easy to have the new group save many other people who haven't very recently learned important lessons through danger they've experienced.
It's like passing your drivers license drive test and then forgetting how to change lanes the next day.
And just because they start to act they way they should have at the end of the chapter, doesn't mean it "addressed" my problem. This isn't me complaining the author forgot about something that was then explained why it wasn't forgotten later, this is the author ignoring characterization for the sake of a cool moment for other characters.
Bleach did this in the Fullbring and Thousand Year Blood War arcs. And those arcs, because of those issues, are so full of plot holes it's not even funny.
As for why I'm being so harsh, it's because I've seen hundreds of examples of this (though usually it's done to make the villains look more threatening), and it means the author is willing to do stupid things to force certain aspects of the plot.
In most stories, that kind of disregard for characterization means before the story ends, it will do something to break my suspension of disbelief.
So imagine you get tired of badly written stories and you finally find a story you begin to really like, then you see it start to do what all the other badly written stories do. It's frustrating, and that frustration only gets worse the more you've seen badly written stories that lead you on and then sucker punch you with a moment so unbelievable you can't take the plot seriously anymore.
After a while, you start to notice the patterns of bad writing and become able to predict it quite early. It's not a guarantee, but the overwhelming majority of these stories do fail hard later on.
I still have hope for this one, but for how much longer is unclear.