you know these comments are all months old but I'm glad everyone else was as completely confused about this chapter as I was
I think what "happened" is that the manga shows something non-literal happening in a very literal way and then kind of forgets to explain what actually *did* happen on a literal level. The earlier parts of this manga in general seem to kind of have a basic coherence problem, but this is the worst of it right here.
That or the entire thing takes place in monster world and this is the only time it ever comes up.
Also it's fucking terrifying! Yeesh.