Dan Oniroku shoujo mokuba-zeme

Nami is a masochistic high school student who is attacked and almost raped by a gang of hoodlums before being rescued by handsome teacher Muraki. The near-miss triggers bizarre hallucinations in Nami, and she imagines herself engaged in various S&M situations with Muraki, in which she is beaten, forced to urinate, and tortured on the titular wooden horse. (Robert Firsching, All Movie Guide)