Across The Nightingale Floor by Lian Hearn

Set in a war-torn, Japan-inspired realm, a young outcast rescued by a noble lord discovers lethal talents tied to a secretive clan that make him a pawn in a ruthless power struggle. As he trains to infiltrate a warlord’s fortress and its notorious nightingale floor, he is caught between loyalty to his benefactor, a forbidden love for a hostage noblewoman, and the demands of the shadowy Tribe that claims him, culminating in a daring assassination and a choice that will define his fate.

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