Me, my Dad and Mum went on holiday to visit other members of our family. A very long drive, almost eight hours. My dad was driving and my mum was doing the navigation.
After a few hours my dad stopped at a fuel station and I got out of the car and walked to the little shop. After browsing some magazines for a while, the top counter got my attention. A lot of porn magazines with nude girls on the cover. While having a TV magazine in my hand I was watching the porno magazines closely. My penis got instantly hard, I checked out another magazine when my dad entered the store to pay for his fuel. I put away the TV magazine and walked back to the car, still with an erect penis.
We started to drive again, after five minutes my erect penis bothered me. I was still thinking about the magazines, and was getting even hornier than before. I quietly unzipped my pants and took out my erect penis and start playing with it silently.
Clearly watching my parents movement I started to masturbate. Every move my parents made I stopped for a second, and then started again. Because I could get caught every second, the adrenaline pumped through my veins getting even a harder erection. After two minutes (felt like 20) I started to pump even harder, I felt I needed to shoot so I stopped for a minute then I started again.
After doing this for quite a while I really was getting so horny, my legs began to shake. So I finished my masturbation session. I watched my penis, feeling the sperm shooting through the shaft of my penis onto the back of my mum's chair. I saw my penis shoot four ropes of fluid, a fifth just spurted out onto the floor of the car. I put back my still erect penis into my pants and zipped it again.
I watched the mess on the chair and the floor and thought about how to clean it. Because I had no tissues or any paper to clean this, I thought about another option. I took a piece of my shirt and held it inside out, cleaned the biggest mess and put it back normally. My shirt was very wet, but I ignored it.
When we got to my uncles place, I watched the back of the chair. There was still a big spot where the cum hit the chair. I just ignored it and had a really nice week with my parents, my uncle and my cousin (more stories about me and him later)
The spot is still visible, but my parents don't know how it got there and never asked me. I won't tell anyway.