It happened last week
I try to stay as fit as I can. Every weekday morning I take a two-kilometer jog before I go to work. The city I live in has a large park where lots of people jog. It was still cool and a little foggy when I set out on my run. I was dressed in a sweatshirt and sweatpants.
I was pretty tired out after about two kilometers, so I took a break and sat down on a bench. After catching my breath, I jogged a little further and decided to stop and take a leak at one of the public washrooms that were dotted along the trail in the park. There was two stalls and two urinals. There was one guy standing at a urinal and from the back looked to be in his mid 20's, and he was dressed in jeans and a sweatshirt. Not being shy, I unzipped my fly and took my place at the urinal beside him.
As I was pissing, I could see him looking down at my cock through the corner of my eye. There was no partition between the urinals and I wasn't standing too close to it, so he had a pretty unobstructed view. Different situations went through my mind as I stood there, my cock hardening. I finished pissing and risked a glance down at his penis. It was erect, and sticking straigt out in front of him out of his fly. It must have been at least 7-inches-long. That was all I needed, and I started wanking my erect dick.
I was so turned on by the situation I was in. I stopped staring at his cock and looked up at the man beside me. He was extremely handsome, with dark hair, brown eyes, and chiseled features. He was obviously in shape. Our eyes met and we stood there, our eyes locked, wanking our dicks. He started breathing heavier, closed his eyes, and with a buck of his hips, splattered cum all over the back of the urinal. I felt it building up too, and with a grunt ejaculated into the urinal.
Just then, another man walked into the mensroom and we both zipped up. We rushed out of the bathroom, thanked each other, and continued on our jogs. It wasn't until later that I realized that we both forgot to flush so there was a good chance the man in the washroom had seen our cum on the back of the urinal.