4-5 stars... I love this series. The character's relationships were just so real (erm.. besides the whole sibling thing) I tend to really enjoy an anime that has good character development. Kinda like Shingestutan Tsukihime, the character development was really good though it could've been a little longer. Anyways, my favorite character would have to be.. kotori or nemu. I enjoyed Kotori's episodes alot, and nemu was pretty modest and heartfelt throughout the whole thing. So in conclusion, I'd put it up in my favorite anime... where, I'm not quite sure, I don't like numbering things as the best, second best, etc.,so I'll just say its 'up there'.
I really wish there was an OVA
or a second season.