Yeah, the movie made some interesting changes, like making the head master a sympathetic character. The manga version of the character was like Killian from The Running Man, putting on a twisted show. As for slutty Mitzuko, I think the closest thing a movie could come to that would have been a characterization like Juliet Lewis's character in Natural Born killers. Even then I don't think they could push the envelope with the sexual content like the manga did. It even pays homage to NBK by entertaining allusions to Kiryama and Mitzuko hooking up.