This movie is about two orphaned siblings, a brother and a sister, who, after being separated for a number of years, eventually find themselves together in Tokyo city. Neither of them have any goals or desires in life and are easily drawn into the world of drugs (and prostitution?), alluding perhaps to their inability to adjust to normal life after the tragic death of their parents.
The brother, inspired by his close friend, shows an interest in the Buddhist ideas of reincarnation and afterlife. After the brother is fatally shot in a drug deal gone wrong, the rest of the movie portrays what appears to be his last dying (+ drug-induced) hallucination of his understanding of what happens after death.
This intense movie takes the audience on a powerful visual/sensory trip that is saturated with the themes of nihilism, sex, drugs, (more sex), and the idea of reincarnation through the view of the Tibetan Book of the Dead.