Sins as Scarlet (Inspector Iwata) by Nicolas Obregon

Former Japanese inspector Kosuke Iwata spends most of his time working divorce cases after his move from Japan to LA. When he sets out to investigate the murder of his wife's transgender sister he gets involved in a dangerous case that takes him to Mexico where he has to confront the dark ways of the people smugglers there.
A good private eye is somewhat of an outsider and Iwata as a Japanese detective is one for sure.His backstory is quite engaging and dark. In fact, this backstory, the number of flashbacks and the way of words make this quite a literary crime novel. This has two effects: one is that this is a thoughtful, haunting read. The other is that sometimes the flashbacks and background cost some of the pacing of the story.
The research that went in this one is very clear and you are taken to the world of LA or Mexico very effectively.