Mima Kirigoe, the lead singer of the fictional J-pop idol group “CHAM!”, decides to leave the group to become an actress, believing that the idol group life is a dead end job. Her first project is a crime drama series, Double Bind. Some of her fans are upset by her change in career, including a stalker known as “Me-Mania”. Shortly after leaving CHAM!, Mima receives an anonymous fax calling her a traitor. She also finds a website called “Mima’s Room”, which features public diary entries that seem to be written by her that discuss her life in great detail. She brings the site to the attention of her manager, ex-pop star Rumi Hidaka, but is advised to ignore it.
On the set of Double Bind, Mima succeeds in getting a larger part. However, the producers decide to cast her as a rape victim in a strip club. Rumi warns Mima that it will damage her reputation, but Mima accepts the part, wanting to be taken more seriously as an actress. The scene traumatizes Mima (as well as Rumi, who leaves the production control room crying). Mima increasingly becomes unable to distinguish reality from her work in show business.
Several people involved in creating Double Bind, including the show’s writer and photographer, are found murdered. Mima finds evidence that makes her a suspect in those murders, based on entries on the Mima’s Room website, and her increasing mental instability makes her doubt her own innocence. Meanwhile, Me-Mania is constantly shown standing amongst the Double Bind filming crew, and his obsessive home life is revealed when he is shown receiving emails from Mima’s pop idol persona through the Mima’s Room website. It is at this point that reality starts breaking down for the viewer as well: in one scene, Mima is revealed by a police psychiatrist to be the split personality delusion of a woman named Yoko Takakura, only for the Double Bind camera crew to yell “Cut”; in another, Me-Mania finally confronts and attempts to rape Mima, stopped only when Mima knocks him unconscious with a hammer; this too is hinted as being part of a Double Bind film shoot. Rumi finds Mima backstage immediately afterward, and Me-Mania’s blood and body are not found on the now-empty set.