User blog comment:Gsimenas/Volume 8 Yen Press naming/@comment-28251580-20160828102002/@comment-6697950-20160829174540

Area is most likely the intended word. Seeing as the vicinity of a town is called the "INNER AREA" system-wise (that's what appears on the player's UI). P.S. Yen Press changed "INNER AREA" to "Safe Haven" despite the former being written in English. Go Yen Press!

So, I'm voting for keep the fan translation. It's more accurate. Though I'm not sure if "effect" is really needed. It could probably be omitted for simplicity's sake.