My father remarried and my sister and I got a new step-sister. She's cheerful and beautiful, but her breasts and ass are hard to take your eyes off... One day, my step-sister seduces me and I lose myself in a physical relationship! What if my family finds out about this...? But my sister-in-law also teaches my serious sister what feels good, and before we know it, we're having sex together behind our parents' backs!