I loved the series, but after the timeskip I dropped it due to FUCKING SAYA.
However I do remember watching the last episode, and Diva's black bodyguard (I forget the name they had for them) threatened Nathan. Nathan didn't even do much, I think some kind of scowl and the other backed down completely.
This was of course in the last episode, so other than that mysterious crap that's it. No more is explained about him.