Twelve Blades in Contempt by Jorden Darrett

To her clan, she is nothing. She will use their contempt for change, and her strength for war. Aiya is a Ginju, a hidden assassin within the Egaishan Empire. As the black sheep of her clan, she grapples for a connection with her deity, ridiculed by her own family and forced into doing their biddings. Chafing under the heavy expectations of her father, a collision with a rival clan provides her with the chance to prove herself. But a grievous mistake causes their plan to backfire, forcing Aiya to choose between loyalty to all she’s ever known or independence for all she’s ever loved. As civil unrest widens cracks in the empire, Aiya must decide for herself how best to forge her path. To protect her brothers and win respect in the land, she’ll need to turn a new leaf and oppose her clan and her empire. She must conspire with clans once held in contempt and reach new heights of power to create a new world of their own, in a world of spirits, deities and conniving lords. Along the way she will be forced to find her place, her morality and her strength. Medieval Japan-inspired progression/epic fantasy, for fans of Mistborn and The Poppy War