Strange Circus is an intentionally ambiguous film, concluding with dialogue along the lines of, "What's reality and what's not?" The sentiment is consistent throughout its entirety.
The film opens with scenes from the "strange circus" of the films title; the art direction immediately reminds one of the films of Shuji Terayama, specifically Pastoral: The Die in the Country-- bright colors abound, the carnies are grotesquely dressed, and there is constant movement. Young Mitsuko volunteers to be the star of the shows first act; a live show of the guillotine. As she walks towards the stage, she begins to narrate the story of her life. We, the viewer, are thrust into her tale of sexual abuse (by way of her principle/father) and physical abuse (by her mother, who's essentially been drivin insane by her daughters molestation).
We arrive at a point in Mitsuko's story where, through a bizarre and existentially sad turn of events, Mitsuko has assumed the persona of her mother, who she accidentally killed. She goes through her school day excited, getting good grades, finally feeling accepted and full, happy even. But as she walks through the hallway of the school, by herself, staring at the 100 percent she has just received as a grade on a test, she stops, and in an epiphanic moment, realizes that she actually received a 0 percent on the test, and that she's not her mother-- she's still Mitsuko.
A quick jump cut shows us erotic novelist Taeko, writing the scenes that we have just seen on screen. Her agent applaudes the work, and asks her to finish the work soon. She is soon assigned Yuji as a sort of "personal assistant" from her editor. Taeko mostly keeps to herself, and Yuji's editor soon reveals to him that he would like Yuji to uncover Taeko's history, any reality that's present in her novels, and any dirt he can get on her so the company can do an "expose" piece (why a company that is publishing an authors books would want to do an expose on her is beyond me, but it's not utterly relevant).
From this point on, Sono constantly shifts between realities, never revealing what the "truth" is in regards to what is actually happening in the story of Mitsuko and Taeko. He pulls out a huge twist at the end, but in the framework of the story, it works. What would normally be a simple gimmick by way of lesser directors such as Christopher Nolan or M. Night Shyamalan, turns into a pivotal plot point that asks more questions that it does provide answers.
And Sono's tale is uniquely his own. While often displaying influences from other directors (the aforementioned Terayama, a little bit of Hisayasu Sato even [all three directors seem to share an obsession with reality vs. unreality, at least in this film for Sono]), Sono still retains a personal sense of story telling which makes the film worthwhile. For being such an abstract story, it's surprisingly easy to follow, so viewers willing to actively watch the film should not fear.
Another interesting point that bears mention is the way Sono handles the sublime in the first half of the film. In the same way Uta Barth's photographs depict banal, largely empty spaces out of focus in order to achieve a higher sense of emotion, Sono's constant blurring (of focus) achieves the same effect, brilliantly echoing the way that Sono himself is "blurring reality" within the narrative structure of the story. The score also extends the abnormal beauty that the film depicts, accenting the emotional states of the characters and the viewer his or herself.
Strange Circus also is one example of a recent wave of films (other most notable examples include the ensemble piece Rampo Noir) that are finally taking the Japanese horror film in a new direction-- in the direction of the ero-guro (or, erotic grotesque). Abandoning the archetypal J-Horror themes (the creepy child with wide eyes or long flowing hair, the jump-scare every ten minutes) and looking back to something rich in Japanese history (as ero-guro essentially began in Edogawa Rampo's books from the early to mid-century), and using the themes to create something new and worthwhile. A step in the right direction indeed, as the film is an all around achievement.