after five years of marriage, my wife became pregnant and returned to her parents' home to give birth. i thought i might enjoy some single life again, but my wife's sister came to help with the housework. it had been a while since we last saw each other, and my sister-in-law was beautiful and stimulatingly mature. i couldn't help but see her as a woman, and being alone in the same house with her made me uneasy. one day, i caught her masturbating and our eyes met, and from that point on, we engaged in taboo sex.