I lay in bed going back and forth between the two pictures I had of my little sister, stroking myself but trying not to climax. I got bold and went to my bedroom door and opened it, then got completely naked and went back to what I was doing.
At 3:01 PM I heard the front door unlock. It was a half hour before she usually came home, but I didn't think much of it, and kept playing with my cock. It was the moment of truth. Was she actually going to let me lick her pussy? That remained to be seen, but I was gonna show her my cock either way. My heart was pounding at least as hard as my hand was pounding my cock. I heard footsteps walking up the stairs. My bedroom door was wide open, and my eyes were almost completely closed, but my right eye squinted slightly open to see her reaction when she saw me.
What happened next almost made my head explode. I was engaged in the kinkiest, most forbidden act of my life. I had been trying to hook up with my little sister all day, and wasn't expecting anything to happen that would minimize the craziness of that, but it did. My mom came around the corner of the hallway, and my eyes immediately opened wide as she gasped and covered her mouth with her hand. I tried to cover myself up, but she got a clear look at what was going on. She may not have seen the pictures I had open on my phone, but there's no way she didn't see the pair of Ava's panties draped over my thigh while i held my boner in my hand.
She turned and ran down the stairs as I quickly threw some sweatpants and a t-shirt on and chased after her.
"Mom, I'm sorry. I didn't expect you home," I pleaded in absolute terror.
She looked at me without saying anything for a long moment, her face flushed red and mouth slightly agape. After an agonizing wait, she whispered, "It's a natural thing, but what if Ava had seen you like that? Did you even think about that?"
I stuttered back, "I thought I had the house to myself for another half hour. Of course I didn't forget about Ava, mom."
"And using her panties? She would feel so violated. All the porn in the world on your phone and you take your sister's underwear. They aren't even lingerie! Where are they?
I pulled the cotton briefs from my pocket and handed them to my mom. She walked up the stairs and I followed her as she went into Ava's room and to her dresser to put them away. As she folded them she suddenly brought them to her nose and looked at me. "Where did you get these?"