The Last Assassin
This is the fifth book in the John Rain series and they just keep getting better. John Rain is a half Japanese, Half American ex C.I.A. agent who is now an assassin for hire, his specialty is death by appearing to be natural causes or accidents. This book reunites him with Dox, a former sniper who also now is a killer for hire, in this story Rain and Dox along with Delilah, a Mossad agent they try to rid Tokyo of it"s most powerful Yakuza and also keep Rain's former lover Midori and his son safe from the Yakuza. This series is fast and the Rain character grows more complex and conflicted with each book, if you like Ludlum or Le Carre this might be for you.