Nightosphere is a term that refers to a race or a type of people as a whole. These people are normal people just like you and me, however, they are often subjects of the Demon Lord or thought to be evil.

Seria is a member of one of such races, albeit only part of her. Now, in a world where she is only trying to survive and live a simple life, she is dragged into the affairs of an organization of assassins mostly comprised of them?!