That explains a lot, it was strange that they weren't attacked more after they got there, they did have that scuffle with that beast but the thing suddenly left maybe it was the charm maybe it was that it already had accomplished what it wanted, or maybe it the fact that the charm was for Riko and Nanashi.
This just makes my heart hurt more, this author is a sadist, he knows how to make things hurt even more. Maybe this is why Kevin Penkin is such an amazing combination for the ost of MiA, he did say in an interview that he was good at making people sad.
@eviljackspicer Like Karyel said it is just to make things hurt more, but it serves too as a narrative device to point how even death may not be the end in the Abyss, that Mitty may not be the complete real one (at least as far as we know) but putting how it seems that even Nanashi felt it was real, the powers that exist in the Abyss clearly don't care for limitations, even if they take their price.