My brother asked me to check on their house while they were out of town for the long weekend, the last hurrah of summer before the kids all go off to school. He had invited me to tag along. As much as I would have liked to spend more time with my niece, Sara, I couldn't bear the thought of being cooped up in their tiny cabin.

Now that she's older, Sara has been calling or texting me more lately, always asking to go to movies or out to eat. It's been fun taking her to try new restaurants and movies that her parents wouldn't want her to watch. Hell, I've even let her drive my new sports car. I haven't even let my brother do that. There was just one problem. I was beginning to have thoughts that an uncle shouldn't have towards his seventeen-year-old niece, and this was the main reason for declining my brother's invitation to go away for the weekend. I'd probably have a perpetual stiffy watching my niece parade around in her bikinis and short shorts.

My best defense was to stay away from temptation, as Sara was already invading my dreams nightly, and I'd have to jack off in order to get back to sleep. It had gotten so bad that I developed a blister on the head of my cock. I even bought myself a sex toy that simulates a blowjob. "Suck it, Sara! Suck Uncle Mark's big fat cock!" I would pant repeatedly as the toy worked its magic. "Ahh, Sara, I'm Cumming! I'm Cumming, Sara!"

Then, and only then, would I be able to get some slumber.

I stopped off for coffee on the way to their house to bring in the mail. I dropped the mail on the kitchen table and sat down to finish my coffee. On the refrigerator door were pictures of the family, and there in the middle was a selfie of Sara and me. It was the Fourth of July, and she was in her bikini. My cock began to stir when I remembered how her hard nipples had gotten beneath the yellow bikini top. God, I wanted to pull them and bury my face in her cleavage.

As my cock got harder, I got the urge to snoop in Sara's room. I went upstairs and stood in her doorway, wondering what secrets my seventeen-year-old niece would have. Surely she'd have a dildo or vibrator hidden in the bottom of a drawer or in an old shoebox. I slid open drawer after drawer of her dresser until I found her panty drawer. I slid my hand to the bottom of the drawer and felt around for something long and hard. Nothing. The next drawer had her bras with the cups neatly tucked into the next.

"She can't be that big," I thought as I pulled one out—thirty-four, E cup, the tag read. I wondered if the bra was part of a matching set and opened the panty drawer again to find it. "Gotcha!" I said as I set it on the edge of the bed and ran my fingers over the silken material. The cups looked massive, and I imagined what Sara's massive melons looked like in them. I pulled my throbbing cock out of my shorts and tucked it between the bra cups, imagining it stuffed in her cleavage. It was enough to make precum start to bead up on the head of my dick.

I dropped her panties when I went to wrap them around my shaft. That's when I noticed a piece of red ribbon sticking out from under the bottom drawer of her nightstand. I pulled the drawer out and found where Sara had kept an eight-inch dildo and a vibrator. The ribbon, I found, was attached to Sara's diary. I opened it to where the ribbon was marking the page and read her last post. "So bummed that Uncle Mark isn't coming with us for the weekend."

I found it interesting that she would write about me in her diary, and started to scan it for any mention of my name. I flipped to July Fourth's entry to see what, if anything, she'd written.

"July Fourth party at Mark's. I took a selfie with Uncle Mark today and almost creamed my panties when he touched the small of my back. His fingertips felt erotic as his hand came to a stop right above my ass. From the moment that we took the picture, I've fantasized about his electric fingers tingling, touching my breasts, my nipples, and my pussy. The thought of it made me gush in my bikini bottoms. I don't know if he even noticed how much his touch aroused me. I thought my nips were going to bust out of my bra cups. I'm definitely going to finger myself silly tonight."

Holy shit! Sara's fantasizing about me, too. I flipped through her diary until I found the first mention of me, which was on her sixteenth birthday.

"I saw Mark's cock today. He was sitting across from me while I opened my presents, and when I looked up, there it was, poking out the hem of her shorts. It took me a second before I knew what it was. He must have realized that it was sticking out, because he sat up right away. Still, I'm going to count it as my first real dick that I ever saw."

I was in awe as I continued to read the rest of her erotic entry that read like a dirty novel.

"Last night I woke from the horniest dream that I've ever had. It was Mark sitting with his dick sticking out of the leg of his shorts. The next thing I knew, I was kneeling between his legs with his erect cock in my hands. I started sucking the tip until it grew hard in my mouth. I suddenly woke to find myself humping my pillow. I couldn't fight the temptation and slipped my hands into my panties, digging my fingers into my pussy while I envisioned Mark's cock plunging deep into my pussy. I seriously thought someone would hear me saying, 'Fuck me. Uncle Mark,' as I humped my hand."

I flipped through to the next entry with my name. It was a few days later, talking about the purchase of her first sex toy. After reading a couple of lines, I started to masturbate with Sara's panties while I read her entry.

"I bought myself something to help me with my infatuation for Mark. I can only imagine that his cock feels anything close to this. I locked myself in my room as soon as I got home and rode it until my parents got home from work. I'm going to go back to the store tomorrow and pick up the vibrator that I saw, too."

I shot a load of cum into her panties as I got to the last line of her post.

"How stupid!" I chastised myself for cumming in her panties. Now I'll have to wash them and bring them back tomorrow. I decided to take the diary with me to read through it while they were away. I stuck the drawer back into Sara's nightstand and carefully placed the bra back where it was before heading home.  

Back at home, I grabbed some Woolite and carefully washed my cum out of Sara's panties and hung them up to dry before turning my attention back to the diary. I stuck post-its in sections in every passage where she wrote about me. It was clear that she had me stuck in her head. One in particular, Sara described taking a shower after each of my visits so she could finger herself with fresh thoughts about me. A few pages before her last post, she wrote. "I can't wait to turn eighteen so I can confess my darkest desires to him. I can only hope that he won't tell my parents, and be open to the idea of being my first." I set the book down, dumbfounded, that she wanted me as much as I wanted her.

The next day, I brought my sex toy with me so I could masturbate on her bed. When I got there, I got undressed before laying out a matching set of her undergarments on the bed. I stuffed a bunch of her panties in the bra cups so they'd feel real as I lay on top of them. Next, I went to their bathroom and grabbed a towel to place beneath her panties. I then squirted some KY jelly into the orifice of the sex toy and tucked it in the crotch of her panties, and proceeded to read one of Sara's steamy sex passages from her diary.

"I had another dream last night. It was so intense and vivid that it woke me. I pulled out my dildo and started to ride it like it was his cock just like I was in my dream. Mark sat on the couch next to me, and I climbed onto his lap, grinding my crotch on his massive, erect cock. I pulled my skirt up, revealing that I wasn't wearing any panties, and begged him to fuck me. Mark kissed my neck and ripped my blouse open. He sucked my nipples while I pulled his long, hard cock out of his pants. I rode my dildo so long and so hard that my sheets were soaked by the time I was finished."

I could have broken rocks, my cock was so hard. I crawled over the imaginary body and sank my cock into the sex sheath. I reached up and grabbed one of the stuffed bra cups, squeezing it like it was her breast as I humped my pocket pussy. The combination of sucking vibrations sent shivers up my spine as I pretended to be penetrating my niece's succulent slice. "Ah, God, Sara. I'm cumming," I groaned.

A sense of remorse immediately rushed in, filling me with shame for what I had done and fear of getting caught with my pants down. I was disgusted with myself for stooping so low as to masturbate on Sara's bed. I quickly put her bra and panties away and tucked her diary back in its hiding spot before cleaning myself up. I did one last scan of the room, making sure everything was in place before leaving Sara's room.

My mind played tricks on me during the drive home. Did I remove all of the post-its? Had I put the diary back the same way that I found it? I almost turned around a half-dozen times to go back and check. I argued in my head that I hadn't missed anything, and my secret would be forever safe. By the time I got home, my emotions flipped again. Elated by the gratification that I received, I began to wonder if I dared do it again tomorrow. The thought of being caught in the act was enough to keep me from repeating my transgression.  

My brother called Sunday night to thank me for keeping an eye on things while they were gone. "The weather has been shit, so we're heading home tonight. Why don't you come over tomorrow for a cookout?" he asked. In the background, I could hear my sister-in-law and my niece encouraging me to join them.

A feeling of dread and fear started to creep in during my drive to their house the next day. Again, I questioned whether I had covered the tracks well enough the day before. My apprehensions were quickly quelled when my brother met me in the backyard and handed me a cold beer. My niece came out shortly after my arrival, saying that she was finishing writing about her weekend.

"Writing about your weekend? What, did you meet a cute boy or something?" I joked.

"Yeah, something like that. We'll just have to see where it goes from here."

I was surprised at how jealous I felt, but I tried to hide it as best I could. "Will you still want to go to the movies with your old ass uncle, or am I being replaced?"

"I'll always have time for you," she replied. "How about tomorrow? We could catch that new horror movie that everyone's talking about."

I nodded, "Yeah. That sounds fun. Let's grab lunch first."

Sara agreed and said that she'd be over around eleven thirty.

Sara came over the next day as scheduled, but said she wasn't in the mood for a movie. "We need to talk about this," she said timidly while pulling her diary from her purse. "I know you were in my room and read my diary. There's a new passage that I think you'll enjoy even more."

She passed it to me and took a seat on the couch.

I sat next to her as I read her last entry.

"I got an alert from the Nest camera in my bedroom. I had put it there to see if my parents were snooping through her things. I never thought it would catch Mark wanking his weenie while reading my diary. I felt myself moisten as I watched him jizz in my panties. Oh, how I yearn for the taste of his cum in my mouth, or the feel of his hard cock inside, pumping in and out as he fucks me. The feel of his warm cum as he fulfills my darkest desires. I long to feel the touch of his hand as they roam over my breasts. I long for him. He is my new obsession! I fingered myself silly while watching the recording last night."

It never dawned on me that there might be a camera in her room. I could feel my face flush as a cold chill ran down my spine. I had literally been caught with my pants down. I opened my mouth to croak out an apology, but Sara interrupted.

"Yes, I also saw what you did on my bed." Sara pulled out her phone and played the video of me on her bed. "Keep reading."

"When I got another alert today. I was shocked to see Mark naked beside my bed. My pussy was dripping as I watched him climb onto the bed. I rushed to my room and locked the door so I could finger myself while I watched Mark on my bed. Lying on my bed with my pants around my ankles, I shoved my fingers into my pussy, trying to match the thrust of his pelvis. I reached under my bra and pinched my nipple while I rubbed my clit with my thumb. I made myself cum when I heard him cry out. 'Ah, God, Sara. I'm cumming,'

"I wanted to talk with you about this before school started, so I begged my dad to head home early, saying the weather was too crappy to stay. Really, all I wanted was to be alone with you, so I could ask you if we could. You know. Try it just once. Maybe if we did, we'd get it out of our system," Sara said quietly.

"What if it doesn't get it out of our system? What if we can't stop? You're in my head all the time. I can't stop thinking about you. I go to bed thinking about you and then dream about you all night, only to wake up wondering when the next time I can see you again. I, too, long for your touch. To see your smile. To feel your warm embraces. Every time that we're together, I'm afraid that I'll blurt out my desire to be with you. I'm smitten with my own niece and can't do anything about it. I've even contemplated moving away, so I could get over you. My desire for you is my deepest, darkest secret. My heart sank yesterday when I thought that you had found a boyfriend. God! What kind of sicko am I? You're my niece for Christ's sake!"

"You're my uncle, and I have the same feelings, thoughts, and dark desires. I couldn't bear it if we walked away, especially knowing that we both want it. Shouldn't we try it, at least just once?" Sara said as she climbed onto my lap and started grinding on me, like she had in one of her posts.

I slid my hands under her skirt and discovered that, yes, she was pantiless, just like her dream. I cupped her ass cheeks, pulling her to me as I hump her back. Our mouths met in a long, lingering kiss. Sara's tongue swirled around mine as we kissed. She wrapped her arms around my neck, pulling my mouth tighter to hers.

I slipped my hand up from her ass cheeks and under her shirt, lifting it so I could lay my eyes on her luscious breasts. Sara's bra strained to contain her titties. I realized that it was the same bra that I had stuffed with panties the day before.

"Is this?"

"Uh Huh. I thought you'd like it, but I have a feeling you'll like these even better," Sara said as she reached behind her to unclasp the hooks.

My cock just about burst out of my pants when her tits came into view.

I sucked one of her nipples into my mouth and swirled my tongue around its sharp little bud as she continued to hump my erection. "Uh, God. Uncle Mark, you're going to make me cum," she moaned. I held her tight, sucking her tit until her orgasm ebbed. "I want it. I want your cock now, Uncle Mark!" she said, slipping off my lap.

I lifted my butt off the couch while Sara undid my belt. She yanked my pants and underwear down before climbing back onto my lap. The warmth of her cunt radiated on my cock as she reached down to guide me into her dripping hole. I could feel her searing desire as she lowered herself onto my shaft. Sara's tight, steamy hole slowly encased my shaft.

"Oh, my God, Uncle Mark," she moaned into my mouth as we kissed.

After riding me through a number of orgasms,...