[M4F] Tempted by things that can't be unseen

It felt like any other Sunday - I was downstairs with your older sister having a beer (maybe one too many beers), half asleep on the couch. For reasons unknown, I decide to drag myself upstairs to use the bathroom.

I swung the door open, almost pulling my dick out already, when I am caught entirely by surprise... You're there, sitting on the floor, legs spread wide, yours fingers deep inside your pussy, eyes rolling back as you finish orgasming.

We make eye contact, no words are spoken. I blink once, twice. And leave the bathroom. My head now spinning. Wow. I can't I see that.

Our story begins.

(Will this be a slow burn cheating scene? Want to adapt it with different characters? Ages? DM me and we can make it work.)