I liked this show, but it could have been so much better.
It starts with Ryouta Murakami, a high school student who misses his long lost (girl) friend who he thought died in a freak accident when they were kids. Then one day a girl who looks just like his old friend, and even has a similar name, transfers to his class. He confronts her and she says she isn't his old friend, but he finds out she is a witch. He then goes on to meet other friends of hers who are witches too. They are being hunted down and murdered by the secret organisation that made them witches and Murakami helps them escape.
This show is kind of dark, with plenty of grisly deaths (most of which were censored in the copy I saw), but it also has some light-hearted moments, either to keep it from being too serious or just for the sake of being weird (is there such a thing as too weird in anime?). I personally would have preferred it to have taken the serious route, but it still works this way as the light-hearted stuff was mostly ecchi anyway, which isn't so bad. The story line was interesting and the characters were well developed (for only a 13 episode show) and the animation was great. So overall, I say, enjoy!