Slutty girlfriend gets plenty of help with studies

It all was really idyllic. The family was at their country house, the guy and his father were doing some work while the guy's girlfriend was reading for her next exam. But then it all started going wrong. The girl asked for help with her studies - and from the father, not her boyfriend! Chemistry started working between them and the father sent his son on some errand. What followed next would probably be best described as an outdoor-gone-indoor taboo fuckfest! Words are useless to describe it, and it goes for how much the bf was upset, too!