Sixteen-year-old actress Rin Asuka takes the lead as high school girl Mayumi, whose face is disfigured by an attack with sulfuric acid. As more unfortunate events occur, it eventually leads her to becoming a supernatural mass murderer.
The setting is Japan in 1978. Mayumi Sawada lives a good life in a small town in Gifu. Her family runs a successful farming business. Her older sister Sachiko is about to be married, and her other sister Yukie does great business at the hair salon. Mayumi also becomes friends with her crush, Seiji Moriyama. A few days before he leaves for college in Tokyo, Seiji takes Mayumi to a pretty area with a view of the whole town, where he gives Mayumi a button from his gakuran jacket, telling her that he wants her to have it. This makes Mayumi happy.
However, that happiness soon ends. One night, when Sachiko and Yukie go to Tokyo, Mayumi decides to sleep in Sachiko's room. Sachiko's ex-boyfriend breaks into the Sawada house, enters Sachiko's room and, thinking that it's Sachiko in bed, pours sulfuric acid on Mayumi's face. He then kills her mother, stabbing her in the mouth, before being shot in the head by Mr. Sawada. Mayumi is rushed to the hospital, and the doctors are able to save her, though since the acid penetrated most of her bone, any further surgery would put Mayumi's life in danger.
Mayumi's two best friends, Junko and Kaoru try to visit her the next day, but Mayumi doesn't want to see anyone. Mayumi receives a phone call from Seiji, who asks if he can come see her. Mayumi declines, not wanting him to see her face. They agree to write letters to each other after he leaves. Upon her return to school, other students spread rumors about her and call her a "mutant girl" since she covers her face with a surgical mask. One day, Mayumi notices a woman in a red coat standing outside her house, who disappears. Things become worse when her father commits suicide as a way of saving the family's debts with his life insurance. Due to the rumors surrounding Mayumi, Kaoru and Junko begin to distance themselves from Mayumi. In Tokyo, Seiji now has a girlfriend, and has stopped writing to Mayumi. Mayumi continuously sees the woman in the red coat, which frightens her.
The next day, a news report announces that two high school students were killed by a woman wielding a pair of scissors. The students are revealed to be Mayumi's friends, Kaoru and Junko. Mayumi goes to their funeral, where she meets Seiji, who is in town until the next day. Mayumi wants to spend time with him one last time so he promises to meet with her the next morning. The next day, Seiji tells Mayumi that the only reason he gave her the button from his jacket is because Junko asked him to, and that he's always seen her as a little sister. She assumes it is because of her face. Seiji denies this, but when she takes off her mask, revealing the disfigured left side of her face, Seiji hesitantly tells her that he's already seeing someone. On the walk back, he ignores Mayumi. The scene suddenly cuts to a blood-covered Mayumi frantically cleaning a pair of bloody scissors with water. A flashback shows the red coated woman running up behind Seiji and stabbing him to death. The flashback also shows the bloody corpses of Kaoru and Junko. It is revealed that the red coat woman is Mayumi, as some sort of alter ego.
With Mayumi's friends' murders, Seiji missing, and Mayumi's odd behavior, Yukie begins to become suspicious of her. One day, Yukie searches Mayumi's room and discovers the bloody dress she had worn when she met up with Seiji. She tells Sachiko. Mayumi realizes that her secret has been uncovered. At dinner, Mayumi hides the scissors behind her, and unmasks herself before taking a drink of her orange juice. However, Sachiko has poisoned her drink. Mayumi coughs up blood and eventually dies. To cover her, Sachiko places a trench coat over her body. Yukie reluctantly helps her clean up the mess. The two sisters bury Mayumi out in the woods. However, Mayumi somehow returns from the grave, and kills Yukie. She then kills Sachiko next. Before falling, Mayumi asks her, "Am I... pretty...?"
As it begins to rain, Mayumi looks up at the sky. A young boy looks at her in horror. She stares back at him for a moment before going after him with an abnormally crazed face. The left side of her face slit all the way up to her ear. After the movie's ending, it is revealed that Mayumi has killed 13 people and injured 53, and has disappeared.Rin Asuka - Mayumi Sawada
Yukie Kawamura - Sachiko Sawada
Mayuko Iwasa - Yukie Sawada
Yosuka Saito - Mr. Sawada
Akihiro Mayama - Seiji Moriyama