This is a bit of an older story as it already happened during the summer.

My wife and I live in the city, and during the summer break my parents in law came over from the countryside.

We had some lunch at our place and then my wife and her parents headed out to do some shopping. I

'm not a big fan of shopping, so I stayed at home.

About five minutes after they left, I decided to make use of my alone time and started watching porn and rubbing one out in my home office. My wife would text me whenever they were done with shopping so that I could start preparing dinner.

With that in mind, I put on my noise cancelling headphones, dropped my pant, and started watching porn.

I don't quite remember what I watched, but when I was around 10 minutes into my jerk off session, I suddenly felt a tap on my shoulder. It scared the living shit out of me. I turned around and it was my mother in law. In a panic, I tried to close the porn window as fast as I could, and frantically tried pulling up my pants again. I didn't know what to say and just mumbled for a bit as I tried to get my hard boner back into my pants.

My mother in law just laughed and told me not to worry, and that she wouldn't tell my wife.

Apparently my wife had forgotten her medication, and she realized this when they almost arrived at the shops. My mother in law had proposed to go get it for her, so that she and her dad could continue shopping. She had used my wife's key to get in our house, but she couldn't find the medicine so she had to ask me. She said that she had called out my name and knocked on the door, but I couldn't make it out because of my headphones.

I walked to our cabinet, gave her the medicine and she went back to join my wife and her father. She was smiling the entire time. I wonder how long she had been watching me before tapping on my shoulder. My cock was rock hard and on full display for her. Luckily she's very easygoing and never mentioned it again, but I do wonder what she thought when she saw me like that.

Since then I've seen her naked a few times as well, and learned that she is very comfortable with nudity and sex in general. But that's of course a different story.