Onna Kishi, Keiri ni Naru.

A century and a half ago, the Human Nation discovered a new continent and established settlements, enjoying prosperity from its rich resources. Across the mountains to the west, demons developed their own civilization, which the humans labeled the Demon Country. Conflict arose as the Human Nation sent an army to conquer the demon lands, sparking a century-long war. Amidst this struggle, a female knight commits an error within the Demon Kingdom and is taken prisoner by orcs. The orcs respond to her with surprising words. The story follows this turn of events in a fantasy setting centered around accounting.