My husband was previously divorced and remarried me. He has an adult son from his previous marriage, whom I began to treat as my stepson. When I heard he was coming on a business trip, I thought it a perfect opportunity and invited him to stay at our home. On the night of his arrival, I felt slightly excited and had dinner with him, then went to bed early. Late that night, I heard noises from his room and secretly peeked inside, only to find him masturbating. At first, I thought it was only natural for a young man, but the moment I saw his cock, my heart began to race. His dick was huge—thick, powerfully erect, and impressively hard, clearly showing the vigor of youth. I was both shocked and aroused. I hadn't had sex with my husband for a while; though his penis was modest in size, it had always satisfied me. Yet after seeing my stepson's cock, I couldn't stop thinking about it. The next morning, after both my husband and stepson left for work, I was alone doing housework, but yesterday's image haunted me. I began indulging in lewd fantasies, gently touching my private parts. The sensation was as if he were fucking me, and I ended up masturbating.