Nobuyuki Shamoto (Mitsuru Fukikoshi) owns a tropical fish business, a modest concern but it keeps him comfortable in his quiet life. A widower, he is married to his second wife Taeko (Megumi Kagurazaka), who most of the time appears to be barely tolerating him, and his daughter Mitsuko (Hikari Kajiwara) doesn't even do that, taking every opportunity to get away from him and spend time with her boyfriend. Tonight, however, she has gone too far as Shamoto gets a call from the local supermarket to inform him she has been caught shoplifting. Mortified, he and his wife head over to try and calm the situation, but the manager is furious - or at least he is until a successful businessman who also has a sideline in tropical fish shows up. He is Mr Murata (Denden), and he is overfriendly...
As the first minute makes clear in its title cards, Cold Fish, or Tsumetai nettaigyo if you wanted the original name, was based on a true story, a notorious Japanese murder case, though co-writer and director Sion Sono could not lay claim to an adaptation that stuck entirely faithfully to the precise facts as he preferred to spin off in his own direction to make his points. Indeed, making points came across as the whole driving force behind this, with entertainment a bonus should you be amused by relentlessly nihilistic scenes mixed with extreme, if relatively realistic, violence, even with the black comedy sheen. This director could be fairly stylised in his methods, but not this time; it was exactly a documentary fashion he was aiming for, no found footage here, more a tone.
That tone telling us, be afraid, there really are people out there who would behave this way, throwing any niceties of social behaviour back in your face, meaning that there comes a stage where the rule book of your community will be forgotten and acting as if you had carte blanche to victimise and attack - psychologically or even physically - someone else was a very dangerous possibility for some. Sion went further, informing us that once you began picking on someone, you are perpetuating a cycle that will see your victim taking out their frustrations on someone weaker than them, and so it will continue: Mr Murata's father bullied him, now he bullies others including Shamoto, just as by the close of the movie Mitsuko has cracked and will likely attack someone else, and so forth.
One issue with that worldview was that it wasn't necessarily true, certainly this kind of mental strain placed on an impressionable mind won't do you much good, but then again being subjected to that kind of pressure would be just as probable to put you off forcing anyone else through the personal hell you have suffered. Not that relentless bullying can do you good, but it can make you understand it's no place for anyone to be, and do your best to prevent it happening to someone other than you, even if it was simply taking care of how you dealt with your fellow human. That said, if Sion had taken that approach to his tale it would seem longer than it was, and at pushing two and a half hours it was quite long enough as we see a family plunged into something approximating a nightmare that made their previous passive aggressive animosity a walk in the park.
Mr Murata charms the Shamotos, as after he stops the manager from calling the cops he suggests they check out his large superstore to see his collection of tropical fish. There is more than that: he also makes it clear he wants Mitsuko to work for him, actually moving in with his other young ladies on his staff and sporting a uniform, taking the teen off her parents' hands. But he wants even more, as seen when he forces himself on Taeko which she gets a kick out of after living with a milquetoast all this time, another example of dubious psychology, though nothing compared to the mechanisms operating in the mind of not only Murata but Mrs Murata (Asuko Kurosawa) as well. Before long the promise of a business arrangement in Shamoto's favour has resulted him in being witness to his new pal's murder of a rival, and it only gets gorier from there as the protagonist's sense of reason begins to shut down, starting with him numbly complying with the maniac then, as indicated above, taking the law into his own hands. As a critique of Japanese discipline it was memorable. Music by Tomohide Harada.