“If you like them so much you wear them,” Sara quipped, flinging the red silk panties across the bed.

I should explain that in my hurry to buy her some Valentine's lingerie, I had overlooked her size requirements. Sara was always fussy about her underwear, everything had to match and fit perfectly. Not only that, but she valued comfort over style. In an attempt to appeal to her more slutty side, I had been seduced by the usual man-made red silk set, complete with suspenders and stockings.

“You just bought these for your own benefit. Unfortunately, I’m not a size 14! I’m a UK 10-12.”

“That's all they had left,” I protested.

I had been imagining how the red satin would look stretched over her girly curves, my cock sliding between her buttocks. I knew Sara liked to fantasize about being a horny slut if she was in the mood. Sometimes she would talk dirty, urging me to fuck her slutty cunt and use her like a whore, which is what she thoroughly deserved. This would usually get her off in quite spectacular fashion. Otherwise, lovemaking tended to be of the more functional variety, like her choice in underwear most of the time. I thought it was a bit of a shame as she was a very pretty girl with a fine figure. All the better to enhance it with some sexy knickers, bra and stockings I thought. Well, that had backfired on me!

Sara sensed my disappointment, and in an attempt to lighten the mood, after all, it was Valentine's night, she had thrown me a teasing challenge. Little knowing how much that might turn me on.

“You really want me to wear these?” I pretended to be embarrassed.

“If you want...”

I didn’t need any further encouragement and slipped off my mini trunks, pulling the red silky panties over my growing cock. They were a bit big for me too, and I’m only slightly larger than her. Curiously I rather liked the extra material, it made room for my swollen balls and stiffening cock, at the same time allowing a puffiness around my arse and between my legs which enhanced the feeling of vulnerability.

“Who’s a pretty Valentines' boy then?” Sara teased. “Does it turn you on wearing my slutty red panties?”

As if to check, she trailed her red fingernails over the cheap satin and down the length of my straining cock. She didn’t need any more confirmation. Sara plucked the girly waistband away from my shiny swollen cock-head, now leaking a single drop of pre-cum. Then she reached her long fingers down between my legs like she would caress another girl over her panties.

“Who’s a slutty tart gagging for it then?”

“I am. Please make me come…” I played along.

“I’m just a tease,” she smirked, “it’s up to you if you want to come.”

I groaned, “Oh please do it to me, I’m desperate for it!”

“Would this help?” she inquired, trailing one hand over my swollen balls, and the other slipping under the gaping gusset and pressing against my bum hole. I flinched. This might be crossing the line.

“Does it help if you’re wet?” she inquired innocently.

“It might,” I replied nervously, “I’ve never been wet before…”

“You can borrow some of mine if you like, since you’re already wearing my knickers,” she offered.

With that Sara reached her hand into her little white panties and inserted two fingers up her aroused cunt, then covered them in her moisture. Holding them up to my lips for me to taste, I was amazed at how wet she was, much more than she was usually. Gently she pulled the silky red crotch of my panties aside and inserted one of her fingers into my anus.

That did it for me and for her. She wrapped the red silk around the head of my cock and squeezed firmly. As she did so with her finger in my arse, I ejaculated into the panties, bubbles of wet spunk issuing through the red satin material and staining it dark. My buttocks clenched around her finger as I groaned in ecstasy.

“Made you come you fucking horny slut!” she crowed.

“Now it’s my turn. Take your knickers off.”

I did as she asked, and watched astounded as she pulled the spunk stained Valentines panties on (over her own of course), lay back on the bed and demanded:

“Now fuck me like the slut I am and make me come in my dirty panties...”

How could I resist.