Machida is the new girl in school. On her first day, she spots two girls that appear to be twins sitting next to each other in class. One of these girls, Kamei, begs to sit next to Machida. Though Machida only wants to be left alone, she is hounded by Kamei, and is even followed into the bathroom. Despite her threats, Kamei refuses to leave her alone, and asks why Machida is so pretty.
Machida approaches Kamei's "sister" to ask her to tell Kamei to leave her alone, only to find that they aren't sisters at all but complete strangers. Machida resorts to violence, luring Kamei away from the school and begins beating her up until a boy from her class, Hibino, stops her. He warns Machida that she doesn't know how to deal with this other girl, and tells Kamei to go away. Hibino tells Machida that Kamei is trying to "steal" her, and that she is biologically abnormal. Machida laughs in his face, but as she is walking away she sees Kamei again, only this time half of Kamei's face has changed, looking eerily similar to Machida's face.
Machida lures Kamei away once again, but remembers what Hibino told her. That Kamei's face changes to that of the person she spends the most time around. She spends time around the girls in school that she thinks are pretty and steals their face. Machida delivers Kamei to two thugs from her old school so they can beat her up again, but by this time Kamei's face has already changed, and she looks identical to Machida. Kamei tells Machida's friends that she is the real one, and that this girl from school has a plastic surgeon for a father who changed her face to look like her. Machida's friends take her to be the impostor, and beat her up instead.
Hibino finds Kamei carrying a beaten up Machida home, and asks if he thinks she is pretty. She says that she does it all for him, for his attention. He says he has no interest in stolen beauty. He says to come see him when she looks like herself again, but she insists that it doesn't work that way. She would have to lock herself in solitary confinement for a long time. She can't help that she "steals" people's faces.
The next day Kamei arrives to school late. When she walks into her classroom everyone is wearing masks. She panics and runs down the hall, but the entire school has masks on. Hibino asks the teacher why everyone is being so cruel to a student, to which the teacher replies that she isn't even a student. She had been attending school without permission for a very long time, but no one knew what to do about it. He suggests that she might be much older than she appears.
Students in masks torment her, chasing her across the schoolyard. Hibino runs to her aid but is too late. Her face becomes distorted and broken, "stealing" many masks all at once very quickly, and she asks for a mirror.