From Chinatown KM:

Nanase Takeshi is a normal high-school student with a slightly traumatic past. You could say he's hard-working but in reality, he really cares about what others think about him. For some reason, he is going out with his childhood friend, Isoshima Kurumi, but otherwise, he's a pretty normal guy. One day, however, he sees a girl wearing a uniform he had never seen before, who had collapsed on his school grounds. She is Aiba Mui and her appearance marks the beginning to a series of weird incidents. She once said, "to be honest, I'm a magic user and sorry......I turned you into one too."