I loved being home for the summer. At least at the beginning of the vacation, while my parents were both still at work and Casey still had another week left of school.
I had the house to myself, which I celebrated, as you might expect, by stripping naked and walking around the house with my cock and balls swinging freely in the crisp morning air.
I strolled around the house, making myself breakfast and watching a bit of TV, occasionally playing with my semi-erect member. It was a very pleasant way to spend a morning and I can highly recommend it.
In truth though, I was actually trying to put something off. I was trying to distract myself from an itch in the back of my mind. I kept pushing it away or trying to ignore it, but it grew more and more insistent. I knew that I was kidding myself that I could hold back from the painful urge building inside of me. I already knew where my little naked walk would eventually lead me.
My sister's room was down the hall from mine, and I had avoided the place ever since she hit her teens and developed something of a nasty streak.
Casey was a senior now, recently turned eighteen, and I would be lying if I said I hadn't begun to notice the way her flourishing body had begun first to fill, and then overfill her clothing.
It was hardly my fault that I could not stop staring at her. She always seemed to be close to spilling out of her clothes. Every corner I rounded in the house she was there, bending over, showing me a sliver of plump ass cheek in her tight little gym shorts, or far too much butt crack to be considered decent when she squatted to get a book out of her school bag. If she dressed that way for school every day, I am surprised that she has not yet been suspended.
Cautiously I entered her room. For some reason this felt riskier than parading around the rest of the house naked. Almost thoughtlessly I found my hand resting atop the laundry hamper by her door.
I wouldn't have done anything really, but they were just sitting there, right on top of the pile. A pair of soft cotton panties. The panties were a pale pink, the very color I imagined her nipples to be. They were light in my hand, barely there, a tiny scrap of a thong that would not cover very much at all.
I lifted them gingerly from the laundry basket, rubbing the thin material between the pad of my thumb and my forefinger. I imagined I could still feel heat where her pussy had snuggled up against this soft material.
I knew what I was doing was bad. But really I blame her. Since I had come home from college and found her metamorphosed from a chubby teenager into a stunning curvy woman, how I saw her in my mind had shifted dramatically. The way she spoke, dressed and acted seemed deliberately intended to provoke a response in me.
I gave the panties a tentative sniff. They smelled like her. At least, they smelled of the citrus perfume she wore. But there was also a certain musky tang I recognized. It was the scent of her sex. Alike, and yet different from girls I had gone down on before.
My exposed, semi-hard dick twitched and swayed from side to side.
I took a last, careful look around Casey's room. No one was there. No one would be home until this afternoon.
Carefully, I stretched the panties and pulled them over my head. I nestled my nose into the part where her crotch would have rested and let the elastic snap tight around my head. The holes where her legs went made a perfect, if odd-looking, mask through which I could see.
I wouldn't say I was proud of what I was doing. I purposefully avoided looking directly at myself in the mirror. But I could not fight the growing urge I had to be close to my little sister. This way, at least, was relatively safe and harmless.
I took a deep breath in through my nose. Her scent filled me. My dick's response was instantaneous, elongating and fattening like a feeding leech before my eyes.
Though my cock was begging for it, I didn't touch myself just yet. That was a special reward for a bit later. Instead, I perused her room, fingering her collections of knickknacks, most of which were from her recent childish past.
There were some signs of her newly sprung adulthood. Some new books and posters, as well as pictures on the wall, but a lot was unchanged from when she had been my bratty teenage sister.
Actually, she was still my bratty teenage sister. But having the number "eighteen" attached to her changed the way I thought about her a lot.
One picture in particular caught my attention. It had its corner wedged into the frame of her mirror. Ignoring the reflection of the naked man with the pink panties over his face, I peered closer. It was of her and her friend Jordan. They had their arms around each other and both were in swimsuits. Jordan was in a green bikini, which displayed her flat stretch of slimly muscled belly. Casey had her more womanly body encased in a blue one-piece. Its plunging neckline, and the high angle from which the selfie was taken, meant that the view into Casey's ample cleavage was deep and enticing.
Using only the flat of my hand I began to stroke the top of my dick. It wagged in appreciation.
Of course, I knew it was wrong to jerk off to my sister, but who would know? Her body had developed into the sexiest I had ever seen, thick in the bust and backside, both of which flared out dramatically from her tiny waist.
It was the type of figure, almost absurd in its cartoonish proportions, no woman could maintain past the first flush of womanhood. Eventually metabolism, age, and gravity would catch up with her, as it did with everyone. So it felt only right that I should appreciate it now, like a fragile blossom before a storm.
I wrapped my hand around my length and was beginning an easy stroke. It was still early in the act, I intended to prolong it as long as I could, but I checked Casey's desk to make sure she had some tissues on hand. I did not want to have to clean up a big mess afterward.
That was when I heard the soft rasp of someone clearing their throat.
Instinctively I spun, dick still in hand, panties over my face.
My sister was leaning casually against the jamb of her door, her cellphone in one hand, its camera pointed directly at me.
"What the fuck are you doing?!" I squeaked.
She gave me a partially-amused frown before saying, "You know, I was just about to ask you the same question."
"Fuck!" My mind raced, desperate to think of some kind of excuse, any excuse to explain away this situation. But every time I dug, right down to the bottom of the barrel, desperately trying to pull up an excuse, the same message kept being dredged up: "Fuck! Fuck! Fuck!"
"Pink is a good color on you," she mused dryly, her attention returning to her phone screen.
When I failed to answer again, the sound of my beating heart seeming to drown out all other thought patterns, she continued, "Care to explain the headdress? It looks familiar, but I can't quite place it. Is it cultural in some way?"
My mind ran in a loop of self-defeating terror.
"It couldn't possibly be your little sister's panties. That would be perverse."
"Um," I fumbled with the words, before finally managing "I'm working on my Bane impersonation?"
When she looked unconvinced I added in a gruff voice with its signature squeak, "You merely adopted the dark. I was born in it."
An uncanny impression, even if I say so myself.
"Maybe it would be more convincing if Bane walked around naked, with his erection in one hand." She thought for a moment and then added, "Actually, that is a movie I might pay to see."
Realizing she was right I yanked my hand off my shaft like it had been burned. Strangely my erection had not lessened during this entire catastrophe. If anything it seemed to flare painfully under her scrutiny.
"You're not meant to be home," I rounded on her.
"You're not meant to be jerking off with your sister's panties over her face, but life is full of surprises."
