Hidden Nexus (Inspector Saito Mysteries) by Nick Tanner (Amazon UK)
'Inspector Sakamoto has a single-minded approach to the solving of the mystery that is presented to him - in essence there is no mystery. This is a simple case of a jealous husband.
Within hours of returning to duty Inspector Saito, keen not to be sidelined by his rival, involves himself in the case and soon uncovers a mass of startling new evidence surrounding the life and death of Yamada Eri. As the body count mounts Saito finds himself caught within the hidden nexus of modern Japan - the unholy triangle that links business with Government and the Yakuza. For once there is no obvious solution as each and every suspect appears to have a cast-iron alibi.
It's only then that an unwitting Sakamoto helps Saito on his way to the final solution. '
http://www.amazon.co.uk/Hidden-Nexus...36097&sr=1-370