The Emperor's Woman — I.J. Parker

She was intended to be the emperor's concubine, but she died at the bottom of a cliff near Prince Atsuhira's private villa. The palace covered up the scandal. Months later, Akitada is drawn into the case when his best friend is accused of plotting against the emperor. Atsuhira, his alleged co-conspirator, refuses to defend himself. The mystery of the lady's death unravels slowly, bringing danger to Akitada, whose household is already threatened by an ill-fated relationship between Genba and a prostitute which leads to his arrest for the brothel keeper's murder.
Surrounded by a cast ranging from outcasts and assassins to noblewomen serving in the inner apartments of the imperial palace, Akitada not only delves into murky palace secrets, but his efforts to solve two murders require him to examine the many roles played by women in his society.