Watching Me Cum

I about to take go into the bathroom when my older sister opened the door looking for a dry towel. She was totally naked and kept asking me to get her one, but since I was able to see her naked I was slow at doing it. I finally got her one and she closed the door on me. A minute later it opened and I went in as she went out. I turned and saw her whole ass was hanging out and I was watching and started to get hard. I started the shower and after washing my hair I started to lather up and playing with myself. I was doing this for a few minutes before I realized my sister was in the bathroom watching me play with myself. After I ejaculated I looked at my sister who was smiling and asked if it was good for me. I smiled and said yes.