Several years ago, when I was still married, my ex-wife's younger sister and her friend used to be at our house all the time. They lived in the same neighborhood and often babysat our infant son. Many evenings, after returning from work and taking a shower, I'd get into some loose, comfortable sleep shorts and sit in the living room, eating dinner and watching tv.
One evening, while sitting up on the edge of the couch eating from my dinner plate perched on the coffee table, I noticed the girls continuously glancing in my direction. Looking down, I realized that by sitting on the edge of the couch, the bottom to the leg of my shorts was hanging way down, producing a big gap in my shorts. My balls were hanging low and they had noticed. Pretending not to notice, I made sure to provide the best view I could while watching their reflection in a wall mirror. They were openly staring at my cock while whispering and smiling. After a few minutes, I went to the restroom, quickly stroking my cock, preparing to take this to another level.
I didn't get fully erect, just well fattened up. Returning to the couch and sitting back down on the edge, I leaned forward, grabbing a magazine off the table. I felt my swollen cock dangling free in the gap in my shorts. Now it wasn't only my balls exposed to their view, now my fattened cock shaft, helmet and balls were fully visible to the girls, and one glance at the mirror confirmed that both of them entranced, staring with mouths dropped open at, what I am certain, was their first completely exposed man-sized cock. Staying in that position, I felt my cock begin to throb and rise from the excitement in the room. Holy shit, this was getting hot!
They had no idea I was watching their reactions in the wall mirror. Clearly, the believed I was unaware of my exposure. I was now almost fully hard, beginning to stick out and up. I knew it was time take a break. Reclining back on the couch, I sensed their disappointment, but knew that this was just the beginning, as ideas began running through my brain. How could I continue to expose my cock to them "accidentally" while remaining "innocent" of doing anything intentionally?