Their Bright Ascendency, book 1 : The Tiger's DaughterK Arsenault Rivera2017

A poison spreads across an ancient land.
The Hokkaran Empire has conquered every land within their bold reach, using the combination of imperial might and sabotage to devastate and subjugate the nomadic Qorin tribes.
Generations later, the decaying imperial line has led to rampant corruption and ruined fields - and worst of all, the demons once kept at bay by the Hokkaran Emperor have taken advantage of the crumbling protection of border walls, and have begun to overrun villages and forests.
But against all odds. a destined pair of warriors rise from the ashes, the last hope of a devastated people and a fractured nation. This is the story of Barsalyya Shefali and O-Shizuka, who are unafraid to face the demons. They will save their world and become legends - or they will die trying.