Fifty Shades of Gei, An Ennin Mystery #46 by Ben Stevens is a four star mystery.
"'A lonely existence,' he said softly. 'You have my sympathy. Are you in pain...? I can give you something to relieve that...'
A bitter smile twisted her full red lips.
'I have been in pain all my life, Ennin-sensei,' she replied. 'What does whatever bodily discomfort I feel now matter?'"
She had met "A member of the so-called 'Crazy Ones', though sometimes they call themselves Yakuza - 'Worthless' - a name intended to portray their complete severance from polite, conventional Japanese society."
This story held just enough mystery to keep my attention.