I don't think Rei is in love with Na. I think he's obsessed with her, which is quite different. To the point that he has gone insane!!! Not to mention the fact that he is infested with black magic. That alone can't be good for anyone's soul or heart.
Rei is Insane, I know he is deeply in love with Na before, but Na loves the Lycan. Now Rei sees Iris as Na. and i think he is more dangerous than decratic. Why are they all over Iris now?