Well, it has a much deeper storyline than the original. In this, a girl becomes a witch, but her friends keep reviving her and trying to get it right. This Kazumi is the 13th, and so far is going well, but she discovers of her past. She gets upset, and it turns out that one of her friends is actually a fake magical girl. This one, with Kazumi, intends to wipe out humanity and replace it with synthetic humans. Everyone but Kazumi, Umika and Kaoru dies, with Niko killing herself, Saki becoming a witch and Mirai going with her, and Satomi being killed by an insane Kazumi. Kazumi then wishes to have a proper soul, becomes a true human. In addition, Kanna creates a synthetic Kyubey from a dead Kyubey, with the intent of it being able to restore their soul gems without using a witch's grief seed. Then, it turns out that it was only appearing clean, but internally it was corrupted. It's generally better.