First, I totally disagree with most of the people here.
Although I don't quite get why they keep on with the strangling thing, I think the concept of this manga is really deep and amazing.
To the person strangling, it's like you hold the person you love's life in your hands. And to the person being strangled, it shows how much the person loves you as to let you go free in the last minute. Not to mention it IS indeed all about masochism, for those who didn't get it. I know it was implicit, but it was like Kaname showed Usa that pain is not necessary because he can feel "posessed" with love itself.
At least I think that's what it all meant.
I also thought Usa's past was beaufiful. Too sad, I know, but his father couldn't bear that he had fulfilled the mother's wishes until the point that he lost control.
I'm not denying it DOES have some lose ends...for instance, what happened to Kiyo, after all? And what about the one-shot? (I didn't understand A THING!)
Oh, and one more totally new thing! You know...I usually HATE manga women, but I don't hate Kiyo. She's actually really nice and if it weren't for her, they would have that distance between then forever.
As for the art...really pretty!
My only complaint, therefore, it's the lack of sex. I knoooow it's shonen-ai, but I was so looking forward to see Kaname and Usa get dirty =/
(And I love the nickname "Usa", it's so tender and lovely!)