I'm a 45-yr old guy who likes to pleasure himself. I'm a home nudist when I can be alone, even for just a few hours. One day, I got home from day shift and got online for a quickie before my wife & my 15-yr old niece (wife's side) arrived. I was sitting naked in front of the PC and was stroking my aching cock to a teen striptease. The young blond girl was very attractive and I wanted my masturbation to last to the end of the video. I separately played my favourite mood music on the media player as it makes everything much more erotic. I was gently stroking my penis with my left hand while caressing my crotch & balls with my right fingertips when I heard an "Oh my God!" behind me. I quickly turned around and there was my niece! She was wearing a shirt that only went down to her belly and wasn't wearing anything else! She had both hands to her face but her fingers were spread so that she could still see me - with one hand around my cock and the other on my crotch. We stared into each others eyes for a few seconds then my gaze slowly dropped down to her brown bushy pubic hair. This so visually aroused me that I started to stroke my erect cock again. I went on like this for more than a minute and my niece, who was still in shock, hadn't moved from the spot or thought of covering herself. Her hands slowly came down to cover her mouth while her eyes would lock into mine, stare at my throbbing cock, look at the video behind me, then lock with my eyes again. The whole thing was so unexpected and exciting that pretty soon I felt I was going to come & I didn't want to turn away from my niece. I wanted to see her watch my orgasm spurt in front of her. Time to time I would lick my hand to lube it up and her eyes would follow. My breathing started to turn to short gasps as I laboured with my strokes and vigorously rubbed my right fingers against the side of my right nut. This method greatly enhances the sensation just around the base of my cock and heightens my climax. I pried my eyes from her crotch and locked eyes with hers. Then my sight glazed over and closing my eyes I ejaculated with a loud moan. I felt my hot cum on my belly and chest and just swam in the delight of the moment. After my breathing had settled down, I opened my eyes to see her still frozen there. I continued to stroke my half-erect cock and asked her to get me some tissues. She backed out and came back still pantyless. She handed me some tissues and ran out, flashing me her cute butt. I apologised to her later, saying I didn't know anyone was in the house. She had come home early as some school activity shortened school hours. She smiled and shrugged "That's OK". I complimented her on her very nice figure and we agreed not to tell anyone about the "incident". After that, when no one's looking, she will point to young teens in fashion magazines, give me a cute frown and wag her finger. I'll put a finger against my lips and lift an eyebrow. She then gives me a sweet sideways smile. ----------------------------------------