Might as well put something here to start, since I'm sure nobody has ever fought a Narukami ever since the beginning of time.
I'd stay above or below him much as you can, this fight is all about avoiding being at level with him and staying out of his reach when at level, at least that how it usually ends up for me that is. Its also not that bad to keep him in the air, just mind the air reversal.
Though the reversal may sometimes clip you on a cross-up, its not that bad since he'll get a small bit of damage and unless its put you in corner, he gets minimal to no advantage whatsoever from it.
Oh, and J.C a LOT.