With my wife in the shower, I couldn't resist the temptation of her sister's luscious, ebony booty. She sat on my lap, her thick thighs straddling me as we watched TV. I started innocently enough, just a friendly ass massage, but my hands had a mind of their own. They migrated to her panties, feeling her warmth, her wetness. She squirmed, enjoying the touch, but we knew we were playing with fire. Any moment, my wife could have walked in, catching us in our taboo act.