My father remarried my single mother and suddenly I had a sister. She wasn't even used to living with four people yet, but since her parents went on their honeymoon, she ended up living alone with her sister-in-law. I have to study for the entrance exam, but I can't help but be curious about my half-sister-in-law's big ass! I got so excited by the big ass sticking out of my denim shorts that I couldn't resist it and fucked her right away.