Thank you all for your reviews! A few ending notes in response to some questions I've gotten:
1) Haru is an original character, and not a particularly important one. What's important is the concept that there have been several attempts made to claim Kurama against his will, and Haru is the latest of these challengers. Hiei kills them if Kurama doesn't manage it first. In this particular instance, Haru knew Hiei would be coming after him and challenged him when he got there, asking why he had not yet claimed Kurama for his own, if it was so obvious he wouldn't let another have him. Hiei didn't respond, but it did make him think. I don't intend to write this scene out, but I am flattered by the requests for it.
2) The fact that Kurama doesn't mark Hiei is deliberate. In this particular fic, marking is not mutual, nor is it a sign of love. One demon marks another as a part of his territory, as belonging to him. The demon who is marked can neither touch nor be touched by another, but the one who did the marking can. It was never meant to be an equal bond, but rather resembles a much more historical view of marriage, where the wife was considered subservient to her husband. A powerful male demon like Kurama would usually be expected to be on the other side of such a bond, but his beauty and soft-spoken manner have made him sought after. The unevenness of the bond may be addressed in a sequel to this, "The Concept of Love."