Only wanted it in the mouth and ass to save her virginity. Brent likely took it too far on day 2 and split apart her previously intact hymen with the black dildo used to prep her anus (hence the object R @PE charge). He kept her naked and bound so it turned into R @PE after the first day. If he would have stopped at binding, throat and anal fucking and then took her back to her dorm the next day all may have been OK. It can be confusing in the moment when both are really into what is playing out and that it was a K-nap BDSM role play where her part is to resist/protest and his part is to be forceful and do as he pleases and I get how it could escalate.
Bet he pleads to only the obstruction charge as all the other charges will be tough to prove in court to a jury with her kinky behavior and history. On cross examination when she has to admit that "yes I am a kinky anal whore but a virgin and should be treated with the upmost care and respect while being bound and anally R @PPED during my role play fetish".