Barry Eisler - Killing Rain aka One Last Kill

No one but Japanese-American assassin John Rain can win the game of cross and double cross he encounters in this new novel of sexy international intrigue in the series.
Torn between his past as a soldier and his vocation as a killer, longing for attachment but forced to operate alone, and haunted by the fear that one day there must be a reckoning for the things he has done, John Rain moves like a dark ghost through Tokyo and the other urban landscapes in which his Asian features enable him to operate undetected. His ability to make death appear to have been of “natural causes” keeps his reluctant services in constant demand.
In Killing Rain, Rain has a new employer, the Mossad – which needs an operator who can remove “problems” in Asia – and a new partner: Dox, the ex-marine sniper and party animal first introduced in Rain Storm. He also has a new hope that by using his fearsome talents in the service of something good, he might atone for all the lives he has already taken. But when Rain’s freshly awakened conscience causes him to botch an assignment, turning what should have been a surgical hit into a massacre, he finds himself running both from the Mossad and from the CIA. Can he trust Delilah, the alluring Israeli agent whom he once fought and then loved, to save him now?