Also known as: 魔王なあの娘と村人A
That Demon Lord Girl and Villager A is a light novel first published in 2011, written under the pen name Yuukirin(ゆうきりん) and illustrated by Akahito.
The story takes place in a school that prepares people for roles in fantasy stories. Including side roles like "villager A".
It has a manga adaptation, written by Yuuki Rin and drawn by Tsucaco.