My SIL was coming over to use our house. I know she was coming, but I was in bed when she got there. She let herself in and went downstairs to do her work.

I woke up, remembered she was coming over, and hatched a plan. I wanted her to see me naked. I stripped my clothes off and since I was horny and wanted to impress her, i jerked myself until I got a boner.

I went to the top of the stairs and yelled out to see who it was. She walked to the bottom of the stairs and didn't make it the whole way because she saw me naked. I never got to see her face.

We held a short conversation as she reminded me why she was there. She never asked why I was naked.

A few weeks went by before she confessed to seeing me naked. I told my wife the story hoping she’d talk to her about my dick. She never has.

My wife occasionally mentions the story and reminds me her sister has seen my dick. No one knows I showed it to her on purpose.