Recently, my married sister came to visit my parents' house for the first time in a while, but she came to my room with a serious look on her face... When I listened to her story, she told me that she was so bad at sex that she was worried her husband would dislike her, so she asked me to let her practice, but she couldn't ask anyone else... Then, confused, she straddled me and became my practice dummy! I was captivated by the swaying tits of my sister in front of me, and I was so excited that I reflexively thrust my pussy up from below, and she changed completely! I had never seen my sister's face turn into a climax with a scream!