"My Sister-in-Law and Her Panties"

My favorite masturbation fantasy is to think of my sister in law while I stroke my penis. She has an awesome body, with a nice flat belly. She has a set of 36D perky breasts and a fantastic perfectly round tight rear end. She's 23 years old and she says she is a virgin. Every time I see her, I look at her butt every single chance I get.

Either she wears very tight jeans which show how hard and great her butt is, or she wears loose fitting sweatpants, which show the outline of her panties hugging her butt. When I'm at her house, I always go in the bathroom to look around and see if she left a pair of her panties laying around. If there is a pair in the bathroom, I always smell the crotch while masturbating to climax. If no one is around, I'll sneak up to her room and look around until I find her burgundy satin panties.

I then take off my pants and slip into her panties. When I feel the orgasm coming on, I take the panties off and stroke my dick with them wrapped around it. I ejaculate onto a sock in her laundry basket.

If that stuff isn't available, I just use my imagination. Sometimes, I get naked in the shower and get down on my knees. I pretend I'm having sex with her doggy-style. I'll hit my hand and arm against my hips to make the sound that happens when a girls butt hits hips my hips when I do her doggy-style.

I imagine that I slide very slowly into her. I love the thought of being the first man she has ever felt inside her virgin pussy. As I start to pump myself, I imagine it feels tight and strange to her, but then as it feels better to her as I start moving faster and harder and deeper into her vulva. Then I start jerking off as fast as I can, as I hear the loud slapping sound so loud. Sometimes, I'm afraid my wife will hear which makes the whole session more intense because I know there is the risk of getting caught. Then, I imagine her cute little voice moaning, "Oooh," as I fill her virgin vagina with my ejaculation. I never get tired of this fantasy. I also never get tired of sneaking a smell of her panties whenever I can.

The only problem is that I am worried that this fantasy can grow because I seem to be more and more obsessed with my ideas. Each time, I am taking more and more risks. The risk adds thrill to the time before I am about to orgasm. But I am wondering how far is too far. I don't want to cheat on my wife, but I feel like I am in the beginning stages of a very specific fetish for my sister-in-law and her undergarments. I would be embarrassed to death if I ever got caught with her panties.

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