It's useless to try to describe the plot of "Paprika". There is one, a rather obvious one, that revolves around the theft of a machine that allows the user to enter people's dreams. The titular Paprika is the alter ego of a researcher who is working on the device. However, this movie is not about plot. Really, the storyline is simply a device used to procure the visual mastery that the film exhibits.
And what a spectacle it is! The film is constantly spinning in and out of dream sequences (half the time you don't know whether it's dream or reality) and from the very opening sequence where Paprika is running through the city shifting in and out of images, Kon exhibits a virtuosic command of the visuals. Color and symbolism are used to create excitement and suspense, and often times the visuals are extremely frightening, as though the viewer is experiencing the nightmares of the characters.
The music is also pretty perfect - the technological score by Susumu Hirosawa is perfectly fitted for this futuristic thriller. All of the technical aspects of the film are weaved together brilliantly to create the dreamlike tone of the film.
Perhaps the film ends a bit too soon, and the pacing is not always perfect, but despite being confused I was never alienated from the action and always felt like I knew what was going on. It was basically like a dream: nothing is normal but it all feels so right.
I don't necessarily love "Paprika" as much as Kon's other works (especially "Millenium Actress") but with this film he has created an exciting and nearly perfect study of dreams and of the human mind, accented by visual spectacles and ridiculously awesome music.