My body has become a mere test subject for the girls to experiment with sex. But because I get an erection so easily, I end up ejaculating according to their commands. I get my breasts squeezed to make them bigger, or I'm sexually teased as practice to make my boyfriend excited. Eventually, they even invade my house and use it as their hangout spot. But just watching these girls relax with their panties exposed is enough to make me erect again.