Blade's Heart

There is something strange happening in the town and the school. People would mysteriously disappear for days only to suddenly appear again. The school hallways would seem to go on forever, but then all would be normal again. It was as if there are two separate worlds which were intertwined together. One day, Ryouji noticed a girl that he hadn’t seen before, but everyone else did not seem to be surprised at all and treated her like she had always been a student at the school. The girl Ouka approached him and said: “You’ve noticed, right? Which side are you on?”