[blueman2021]

My wife and I lived at my MIL's house.
Every now and then MIL's sister would be in the house for a few days. It was pretty early on when we lived there.
There was a large bathroom with 2 showers side by side separated by curtains. My wife and MIL were not in the house at the time. As usual, I went to the shower after yard work. Stupidly, I walked into the shower room naked with only a towel wrapped around me, thinking I was home alone. As always I used the back shower and when I was done I heard someone come in. The water had already been turned off and the curtain had still been drawn. Since it was still quite light, I hadn't turned on the light yet. It couldn't have been my wife and MIL, I knew that. So it can only be the sister.

She was around 45 at the time and I was 22. She had a sexy body with everything that goes with it!
I heard her undress and go into the shower. Unfortunately my towel was hanging on the wall hook about 2 meters to the other side. I was getting nervous and worried that she might hear me. So I pulled the shower curtain aside and looked for the other shower. Unfortunately, she hadn't closed the curtain all the way, so I saw her standing. She washed her body and turned around. Phew I thought what a sight. But how do I get out of here undetected?
Because I liked what I saw, I got a slight erection.
So I had to get out of here, but how? So I hoped that she would wash her hair. And indeed she started with it.
Finally I saw my chance to go out. But since the floor was tiled and my feet were wet, I immediately slipped and hit the floor.

She heard it, of course, and pulled the curtain all the way aside, looking at me in horror. I felt like a peeper and was now lying naked in front of her on the floor with a half erection.
But she immediately asked me if I hurt myself. Then she even got out and helped me get up. Also naked. I tried to explain to her how it came about but she just waved it off and laughed! She raised both arms in the air so that her breasts were pulled tight.

It remained a secret for both of us for a long time and more "incidents" were to happen.