Since it’s not in the same place in the manga, here’s the specific short, self contained except from the LNs where the red person first really appears. This is the first text in LN3 case file 9 Yamanoke Presence - so seven case files before where we are now.
Thanks for sharing! I guess the story works without having this mentioned as well, though it's too bad we missed the bit about her thinking it was her mom.
And you make a good point in that it might not only be this babble. I'll reread the army rescue chapter next and share my thoughts, Toriko and Sorawo do make a call from the Otherside in there.