Secret Session

One afternoon while my mom was working, me and my sister were in the living room. She was at our desk working on the computer, her back facing me. I was watching the TV when I got horny. I took out my phone and look up some porn with the audio on mute. I make sure my sister is really distracted and put my hand in my pants. Started mastubating whith one hand holding the phone. I orgasmed and resume watching TV like nothing happened. My sister never noticed anything since she had her headphones on and I was happy.