This is not the kind of movie you recommend to people, this is the kind of movie you warn people about. It became legendary when Charlie Sheen notified the police, apparently thinking this was an actual snuff film (which might just be an urban legend). Fact of the matter is that after watching Flowers of Flesh and Blood, that story sounds a lot more plausible.
The story is notable in its absence. A guy dressed up as a samurai kidnaps a woman, sedates her and cuts her to pieces. Limb by limb, slowly and methodically, with pretty much everything happening on screen. It's numbing, it's graphic, but those with a taste for gore will also be incredibly fascinated by it, because it does look surprisingly lifelike.
Flower of Flesh and Blood isn't a film you can judge on cinematography, performances and/or plot. It's an experiment in visual effects and graphic horror, extremely disturbing but also extremely effective. It's niche/cult material at its most extreme, but it's infinitely more memorable than most of the films I watch. Essential viewing for the true gorehounds.