User blog comment:Krayfish/Temporary Leave of Absence/@comment-5870856-20150209184105/@comment-1743498-20150308031321

Basically, the miasma makes any adult sick for some time before becoming paralyzed in a zombified state. Only the aura from a fairy can neutralize it, but so far, only four fairies are known to exist, and they currently make the cities possible in the first place. With the adults effectively trapped and most children too scared to do anything, the protagonists really struggle to find allies.

As for the area the miasma encompasses, I never really specified since all the major events will take place in an area equivalent to a small country. But given the state of this area, the characters consider it their entire world anyway since they know next to nothing about what's beyond.

While I was away, I did have time to think about some possible revisions to the unreleased chapters so I still have the chance to mold it and respond to feedback.