She Catches You Looking At Her Butt - Horse TF (Patreon)

You were hanging out with your girlfriend and her sister. Your girlfriend went to the bathroom. Then something happened to her sister.

The sound of her jeans ripping was so loud. You snapped your head over and saw her enormous ass growing. Then she catches you looking at her butt and gives you a disapproving look. She's completely unaware of her changes.