Pure Club is a popular idol group beloved by people all over the world. However, some fans harbor darker feelings than just love—something Karen Amamiya comes to understand all too well when a hooded, rain-soaked man cuts her arm at a handshake event. Following the incident, Karen quits Pure Club and disappears from the public eye.

Nina Kamiyama is a girl who doesn't want to look feminine at all, cutting her hair short and opting to wear the male uniform at her high school. But soon, a girl at a nearby school is assaulted, so all the high schools in the area cancel the girls' after school activities, urging them to walk home in groups. Hikaru Horiuchi, a boy in the judo club, sees that Kamiyama is still walking home alone, despite the school's warnings. One day, he stumbles upon Kamiyama as she is walking home and discovers her secret: she was Karen, the former idol in the center position of Pure Club.

But Horiuchi isn't the only one who knows about Kamiyama's former life—her assailant does too, and he is lurking in the shadows, waiting for the perfect time to strike again.