I really don't know what's going on. All I can understand is that some privileged high school kids with some awesome spiritual powers get to go to the best high school ever and have some weird disputes that I just don't understand. There hasn't been a single answered question so far even though we're more than half way in; in fact, they're just making us ask more and more questions every episode. Who the hell is Izumiko's mother? Why is Miyuki so weak? Why does the anime go from one crappy plot point to another without explaining anything? Who is Takanagi or whatever? Who are Mayura and Manatsu? What the hell is Masumi? Why do they care about a dying horse so much? Why do they fight? What the hell is up with spirits? Why is there a fan club for Mayuri? Who was that weird guy that asked Izumiko's to dance for him? Who is Miyuki's father? Who is Izumiko's father? Why is the anime named Red Data Girl? I just can't make any sense at all of this anime.
Art: This is the only good thing I have to say about this anime. The art is good, one of the best I've ever seen. Though I have no idea why the characters except the main two look so bland and unmemorable.
Characters: the main character seems like she could be interesting, but she's barely in the plot at all. She barely does anything. Miyuki seems like he could be interesting but he just turns out to be a bland boring typical stern anime character. What the hell is up with Masumi, Takanagi (is this how you spell it?), the person who asked Izumiko for a dance, and Wamiya? Why are the Souda siblings so important? Manatsu is just bland and boring. Mayuri is too to the same extent, but she's also a bland boring moody brat. There's nothing likeable about anyone here.
Plot: As I pointed out earlier, the plot doesn't make sense. It just jumps from one thing to another without explaining anything. It just is plain bad writing. Worthless.
Overall: probably the worst anime I have ever seen--more than even Aku no Hana. 2/10 for good art.
