I've actually read all 4 volumes with a tearjerking moment everytime. I love it, no worries, but I have to be not bias here... This series is quite good. The art is how CLAMP should've stayed with. It's good, and it actually shows how cold-looking the characters, are but in the end, try to reveal their sweet side.
Kohaku's relationship with Shuichiro (I hope I got it right) is a perfect blend. Sure she's not perfect, but that's what we love about her.
Favorite characters? None. I love them all.
What is missing? Well, nothing really. Though I do wish for an anime version of this manga.