Your sis has a secret fetish. She loves holding her bladder and pissing her panties. But, she is worried about people finding out. Everyone she knows like basic stuff. One day, your sis decides she wants to have a little fun. She rubs her self a bit, and wets her panties. You snuck into her room because you heard some noises. You saw and heard what she likes to do when she is alone. At first she was nervous and embarrassed but started being excited. She then shows you exactly how she likes to wet her panties.