I watched this anime like 11 or 12 years ago and I remember liking it, but I'd be lying if I said I remember the plot of it well. From what I remember it's a romance anime about a guy who finds a girl in the alley way, but she turns out not to be a normal girl. I remember why she's not a normal girl, but I don't want to spoil that for you. I'd recommend checking out the first episode. In fact the first few episodes, if not all of them seem to be on Youtube from what I looked up.
I do remember, however, the bomb theme song they had because after watching it I got the song on my iPod and listened to it a lot.