Satoshi Kon is a Japanese animation film director whose works, story, and imagery suggest altered mental states, such as insanity or dreaming. Millennium Actress (2001), which this author regards as Kon’s magnum opus, uses a dream-like style of animation and filmmaking to create the narrative of a biography of a fictional actress. In this feature-length animated film, Kon reifies theories and findings from the functions of dreaming and the mechanics of dream that have developed over a hundred years since the early 20th century. The oneiric quality of the animation film is explored using both psychoanalytical/psychological theories and neuroscientific frameworks to reveal its story of a feminine journey in relation to the collective unconscious and mythic story structure, and the cinematic editing techniques that help the storytelling lead to the dream state.