My girlfriend and I were going on our first holiday together, so we had to get a five hour train. We were saying before that once we got to the hotel we would have to have sex in the room immediately, so we were excited to get there. On the five hour train journey there was only us and another couple in the carriage. They were a bit older, maybe late twenties or early thirties, already on the train. She had jeans a very tight tank-top on, and he had on jeans and a tight t-shirt. We sat away from them and then the train left the station.

About half an hour into the journey, I heard quiet moaning sounds from the other couple. I slowly turned around and saw the woman had her legs open, and the man was rubbing her through her jeans! I looked around and saw there weren't cameras on the train, then I turned back and told my girlfriend, and she slowly peeked at them too. The woman had lifted her tank-top up, wearing no bra and started to play with her nipples. My girlfriend bit her lip as she turned around and said that doing public stuff like that was a huge turn on for her.

I hadn't told her but it was for me too, and I was already starting to get excited thinking of us doing public stuff on our holiday. She continued to secretly watch them, and I could see she was squirming in her seat too. I decided to take the chance and, like the other man, started rubbing my girlfriend through her leggings. Immediately she started breathing heavy and I could feel she was already a bit wet from watching them too. She returned the favor by rubbing my already hard dick through my jeans, and she started to moan too.

The other couple must have heard us, because after that they took it further. I turned around to see them and she had his cock out jerking him off, while she had her jeans pulled down so he could finger her. I saw the woman look at me, then she whispered something to the man, who grabbed her head and pulled her down to suck his cock. The sound of her gagging on it got my girlfriend a lot wetter, and I reached down her leggings and fingered her. The train was full of gagging and moaning sounds from the two ladies.

My girlfriend lifted up her top and pulled down her leggings and I undid my jeans. She was about to suck my cock when the couple came over to us and sat across the table from us. I started to pull my jeans up but they said not to, so I left them down. They introduced themselves to us and asked if they could watch us do stuff. I let my girlfriend decide and she said okay, so then she started to suck my cock while I kept fingering her. It was odd having somebody watch us, but they were still playing with each other too. My girlfriend wasn't too good at blowjobs, so the woman started giving her tips as she went, like "lick it like it's an ice cream", "use your hand while you do that" and "the sloppier the better".

It definitely helped and soon I felt I was going to cum. But then the man told her to stop, and she did. He told us they wanted to see us fuck, so my girlfriend said okay, and she took off her leggings and thong. I stood up and she bent over the seats doggy-style, her arms on the table. It was helpful that the blowjob was sloppy because I was able to slide my cock into her easily and started slow. It was difficult trying to stay in her pussy while the train was moving and I was trying to fuck her, so I grabbed her hips and pulled her onto me (which I knew she really liked), and she moaned loudly as I went faster.

The couple were just watching, she was stroking his cock, and he was rubbing her clit. I started to go deeper and my girlfriend said she was going to cum. I could feel her legs shaking, so I kept going as deep and as fast as I could. Then, when she couldn't hold it any longer, as she started to cum on my cock, the woman kissed my girlfriend on the lips and the guy leaned over and smacked her ass! She moaned really loud while kissing the woman and I could feel how wet she got around my cock, and I was about to cum too. When I said I was, the woman stopped kissing my girlfriend and then kissed me instead, using her tongue and biting my lip too. I pulled out and was going to cum on my girlfriend's ass like I usually do, but she turned around and took all my cum in her mouth, then swallowed it. The woman suddenly stopped kissing me as the man grabbed her head, pulled her onto his cock again and made her swallow his cum too. We all sat there for a while, sweaty and out of breath.

That's how my girlfriend and I started getting into public sex, and we still meet up with that couple from time to time and have some fun. They send us pictures and videos of them fucking in very public places with the words "Bet you can't do better!"