The film takes place over six days, with footage from a fictional pop group "Dessart" opening and closing the film.
In Tokyo on May 27, 54 teenage schoolgirls commit mass suicide by throwing themselves in front of an oncoming train. Shortly after, at a hospital, two nurses commit suicide by jumping out of a window. At both locations rolls of flesh are found, with the missing skin matching removed flesh on corpses. Three detectives — Kuroda (Ryô Ishibashi), Shibusawa (Masatoshi Nagase), and Murata (Akaji Maro) — are notified by a hacker named Kiyoko (Yoko Kamon) of a link between the suicides and a website that shows the number of suicides as red and white circles.
On May 28, at a high school, a group of students jump off the roof during lunch, sending the city in search of a "Suicide Club".
On May 29, the suicide boom has spread all over Japan. Mitsuko (Saya Hagiwara) is on her way home when she gets hit by her boyfriend, Masa, who has thrown himself off a roof. Mitsuko is taken to the police station for questioning, where the police strip-search Mitsuko and discover that she has a butterfly tattoo.
On May 30, the police receive a call from a boy who warns that on that evening at 7:30, another mass suicide will take place at the same platform. The detectives organize a stake-out in order to prevent the event, but there is no suicide. Meanwhile, individual and smaller-scale group suicides continue all over Japan, claiming many lives, including Kuroda's entire family. Kuroda receives a call from the boy who warned them about the second suicide wave, and upon the conversation's conclusion Kuroda shoots himself.
Meanwhile, Kiyoko is caught by a group led by a costumed man named Genesis whose hideout is a small subterranean bowling alley, where he resides with four glam-rock cohorts. During her capture, Genesis performs a song while a girl in a white sack is brutally raped and killed by one of the henchmen right in front of them. At Genesis' lair, Kiyoko e-mails the authorities information about her whereabouts. The police arrest him, and it is assumed the "Suicide Club" is caught.
On June 1, Mitsuko goes to her boyfriend's home to return his helmet, where she notices the Dessart posters on the wall and recognizes a pattern which corresponds to the letters on a Telephone keypad and spells the word "suicide". Soon, the boy from earlier calls her to tell her there is no "Suicide Club" and to invite her to a secret concert.
On June 2, Mitsuko sneaks into the backstage area, where she wanders onto a stage. She sees a group of children in the audience, who ask her a series of questions. Mitsuko impresses the children, so they take her to a room where a strip from her skin is shaved off, where the butterfly tattoo is.
A new roll of skin ends up with the police, and detective Shibusawa recognizes the strip from Mitsuko's tattoo. That evening he sees Mitsuko as she is standing at the train station and grabs her hand but she pulls away. She stares at Shibusawa as the train pulls into the station and once she boards the train. As the train pulls out of the station the ending credits segment begins, in which Dessart announce their group's disbandment and offer appreciation toward their fans' loyal support, before performing their final song.
The film has an approval rating of 50% on the review aggregation website Rotten Tomatoes, based on 6 reviews. Jonathan Regehr of Screen Anarchy gave the film a rating of 6/10, calling it "an unbalanced movie". Dai Green of HorrorNews.net wrote that the film "may not register entirely in first run, but it will certainly leave a mark". Virginie Sélavy of Electric Sheep Magazine wrote that "Suicide Club has been described as 'muddled' and Sono criticised for not making his satire of pop culture and denunciation of the media clear enough. But the ambiguity of the film is precisely what makes it interesting".
As of early 2006, the film has one prequel and a proposed follow-up. Noriko's Dinner Table (Noriko no Shokutaku) depicts events from before and after the happenings of Suicide Circle and gives more insight on several plotholes of its predecessor. In 2006, Sono said "I always wanted to make a trilogy but in reality it is very difficult."
Jisatsu Saakuru: Kanzenban (自殺サークル 完全版, translated as Suicide Circle: The Complete Edition) was written by Sion Sono in April 2002. The book deals with the themes of Suicide Club and Noriko's Dinner Table, bringing the two plots closer. So far no plans for an English edition have appeared.
A manga of the same title and written by Usamaru Furuya appeared at the same time of the movie's Japanese DVD release. Although Furuya's intention was to faithfully reproduce the film's plot, Sono asked him to write his own story. As a result, the Suicide Club manga is much more straightforward and easier to understand than the film, and features much more solid character development. It deals with the same opening scene, but there is a twist: out of the 54 suicidal girls, a survivor is reported: Saya Kota. Her best friend, Kyoko, must now unveil the secret of the Suicide Club and save Saya from falling deeper into it.