Did the director imply... (Spoilers)
That the first sexual interaction between the older sister and the college student was in fact sodomy? The man licks his hand and puts the spit on the tip of his penis. I thought that with the amount of foreplay going on, he should have been able to penetrate her vaginally with no problem. (though he was rather well endowed and she was a slender, small female)
The next time the couple has sex, the man implies that this will be "there first time". The older sister also screams and is clearly not enjoying herself during her first sexual experience, but later makes no such painful sounds. A very difficult film to watch, but I am not upset that I did. (I did some hard thinking about how I have treated females with regards to sex, esp. in my youth)
"Give up a dollar for Jesus!" Esa Hawks