User blog comment:Omega natsu2/Chapter 369: The Place Prayers Reach, Predictions./@comment-2214433-20140129011112/@comment-7418318-20140130201445

And now that Zeref wants to wipe out mankind, he grudgingly follows those orders and allied up with the Demons even though he dislikes it. That is a nice theory.

But on the other hand, it would still neither explain his similar scent to Gray, nor his dislike for him.