The Masuda Affair - Akitada Mysteries, #6

Still grieving the death of his small son, Akitada risks career, freedom, and family to rescue an abused child from a life of misery.  The search for the boy's family leads to a harrowing story of love, murder, and abandonment.  Meanwhile, his faithful servant Tora loses his new wife to a powerful man who pursues beautiful women and will stop at nothing to posses them.  The trails of both cases lead to the prostitutes and courtesans of the amusement quarter, and murder soon follows.