I agree with the others, basically. The characters and situation are very unrealistic. Girls getting caught up in an abusive relationship could be an awesome topic, but it's difficult to believe these two just put up with being randomly assaulted, especially as the narrator apparently knows the boys are "sick monsters", and react so lightly. Plus, don't they have parents who are going to see their daughters are covered with bruises?
I think you really need to focus on your characters and their motivations, and what you want to portray in this story.