Have only just finished series 2 as I wanted to re-watch series 1 to remind myself of characters plot etc.. But struggled with it, until I watched Shogun (??!!) and then I got going.
Was really glad they started series 2 right after the end of series 1, and only moved the time forward in episode 2 or 3.
Unlike everyong else as far as I can judge from comments I thought series 1 was much better. I think series 2 was more formulaic and probably suffered from fan response to characters.
There wasn't the balance created by using Jake to go out and talk to every day people, and the inner workings of the Yakuza, as series 1 did.
And although not guessing exactly the end it was signaled by about half way through.
I thought they had set up it by the end of series 2 for a third, but see up thread a PP has said not series 3.
Really liked both the wife and mistress of Tozawa!
But still disturbed by the whole nightclub hostess set up.
And will never forgive Jake for letting down his sister. 
And not even a scene to show him phoning.