Nobuyuki Shamoto is the quiet and unambitious owner of a Shizuoka shop specializing in selling tropical fish. His home life leaves much to be desired, as his daughter Mitsuko is rebellious and physically abuses her stepmother Taeko, his second wife. One night Nobuyuki is summoned when Mitsuko is caught shoplifting at a local supermarket. Yukio Murata, a patron at the supermarket, persuades the manager to drop the matter and invites Nobuyuki to visit his own, larger tropical fish shop. During an impromptu tour of Yukio's shop, Nobuyuki meets his wife, Aiko. Stating that fate brought the two men together, the gregarious Yukio convinces Nobuyuki to go into business with him. Yukio also takes on Mitsuko as a worker in his shop. The film concerns quiet and unambitious owner of a tropical fish shop whose life and family are taken over by a fellow fish entrepreneur who happens to be a serial killer. The film is loosely based on the exploits of two Tokyo serial killers, Sekine Gen and Hiroko Kazama, a husband and wife duo who owned a pet shop and murdered at least four people.
Following Alien vs Ninja and Mutant Girls Squad, Cold Fish is the third film to be released by Nikkatsu's Sushi Typhoon, their gore-themed series. Director and writer Sion Sono was influenced by Japanese crime cases while developing Cold Fish, specifically about an actual killing spree committed by a dog kennel owner in the 1980s. Sono also wanted to "depict a sense of total hopelessness" which he felt is "lacking in Japanese films."
Film Business Asia gave Cold Fish an 8 out of 10 rating praising the actor Denden who without his "tour-de-force performance...Cold Fish may never have worked." The review went on to state that "Though there's considerable gore on display, it's largely cartoonish. Cold Fish is not so much a blood-and-guts horror movie, more a danse macabre about social breakdown." In the United Kingdom, Total Film gave the film a three out of five rating, suggesting that plot twists and black comedy offered welcome reprieve from the "largely hysterical acting and rivers of viscera." The Guardian found the film to be "fairly ordinary" in comparison to Sono's other works and felt that the film was too long. Radio Times gave the film three out of five stars, praising the acting from Denden, Fukikoshi and Kurosawa and Shinya Kimura's photography and Takashi Matsuzuka's production design which made up for "some overindulgent directorial moments".
