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The Tunnel	By : PineWreths Category: +G through L > Gravity Falls Views: 9596 -:- Recommendations : 0 -:- Currently Reading : 1
Disclaimer: I do not own Gravity Falls, nor the characters from it. I do not make any money from the writing of this story.

Chapter List
- 1-The Tunnel
- 2-Part 2
- 3-Part 3
- 4-Part 4
- 5-Part 5
- 6-Part 6
- 7-Part 7
- 8-Part 8
- 9-Epilogue
- 7
- 8
- 9
The ride back from Watermania was soothing; Dipper and his sister had to be careful to not linger in each other’s eyes for too long with Soos right there driving, but he was fairly preoccupied with singing along to his Queen CD, and so he and Mabel were able to brush hands a few time with their chauffeur none the wiser. They even sang along when Bohemian Rhapsody inevitably came on, belting out “Beelzebub has a devil put aside for me, for me, for meeeee!” as they pulled off of the interstate.
Soos was leaving after dropping them at their house, but he insisted that they come and visit the Mystery Shack for winter vacation. The twins wholeheartedly agreed, and with a brief honk of the van’s horn, their friend pulled out of the driveway and drove off. Dipper grabbed and squeezed Mabel’s hand one more time, before pulling out his keys and opening the door.
Inside, their mother was sitting in on the couch watching the news, and made a bad joke about “not expecting to get rained on in a waterpark!” The twins groaned appreciatively, and their stomachs did the same when they moseyed on by the kitchen. Their dad had made some kind of tuna-noodle amalgamation that smelled and tasted amazing despite looking like it had already been eaten and regurgitated; Most of their dad’s “meal experiments” ended up like that anyways, delicious yet visually repulsive.
After dinner, though, Dipper had hoped to hang out with Mabel, to be close to her after their experiences together that day, but she had scampered out. As soon as she finished eating, she hastily excused herself from the table before taking a quick shower and then locking herself in her room right away afterwards.
Nonplussed, Dipper cruised around on the internet a bit, double-checked to see if the paranormal forums he frequented had any new sightings in central Oregon, but as he saw the clock tick past ten o’clock, he sighed and shuffled towards his bed, dreading having only one more day to relax before having to go back to his boring job as a retail cashier.
He spared a final glance towards Mabel’s bedroom, where to his surprise her light was still on. He shrugged, though, figuring She’s probably telling Candy and Greta about a “new” boyfriend or something, he thought with a smile, and he pulled his door almost shut before rolling into bed, his covers forming a warm heap as he fell asleep almost immediately.
He awoke to darkness, and a poking in his side. “Erghph, stoppit. Wannasleep go’way,” he mumbled as a foggy glance at his clock said in red lights 12:50AM.
He tried to roll back over, but Mabel’s low, insistent voice said “Dip, c’mon, wake up. Please?”
His eyes popped open, and he rubbed some sleep out of them as he spun his legs around to dangle over the side of the mattress. Mabel was sitting in his office chair, wheeled next to his bed, and to his surprise, she still had her bathrobe on?
A little thought began to send pleasant suggestions of what was under said robe, or rather what wasn’t under it. and he could feel his cock twitch sleepily in response, but Dipper’s immediate attention was on his sister’s closed hands, which she held out towards him.
“Close your eyes.”
He did as instructed, and a moment later she said “Alright, open ‘em!” There, on the palms of her outstretched hands, was a tiny Journal 3, looking almost just like he remembered it.
He could feel his throat tighten for a moment, as he said thickly “Aw, Mabes, you, you really didn’t have to-” but he stopped as he held it. It felt weird, different, and he made a puzzled noise as he turned it over in his hands. Mabel broke out into a wide grin, and she explained.
“It’s craft foam! I had to superglue some bits together, and scrounge up a sharpie from that cabinet where mom locked them when I was in 4th grade, but now you have a new mini-journal. You can’t write in this one either buuut it’s completely waterproof!”
Dipper let out a quiet laugh of amazement, still turning it over in excitement and feeling relief from a last knot of tension he hadn’t even been aware he was still holding on to. His attention shifted, however, when Mabel stood up, shyly looking at him and playing with the cords of the bathrobe’s terrycloth belt.
“Sooo,” she said with a hint of nervousness, “I kinda-sorta-maybe picked out something else while I was going on my ‘Watermania Shopapalooza’ last week.” As she said that, she tugged the robe off and let it fall at her back.
Revealed was a light green teddy, the lacy material cupping and accentuating the curve of her breast as the gauzy material below was plainly transparent and hid nothing. The robe must have still been damp, and he could see where areas of the sheer fabric clung to her form. Below that was a pair of lace panties, a little heart cutout in the middle of the fabric, teasingly revealing an area of smooth skin.
Dipper lost track of his senses for a moment, his attention engrossed in this dream vision of his sister that surpassed anything his mind had been able to conjure before today. The moonlight from the window seemed to frame her lithe form, and she seemed to glow as he watched her.
“So, um, do you like it?”
Dipper said nothing, but temporarily regained motor control as he stood, and pulled her towards him before diving into a kiss. She let out a happy sigh, returning the kiss wholeheartedly, and reaching around to his back with one of her hands. It roamed up under his shirt, feeling the ridges and occasional scars along his back and side, before she ran the hand along his stubbly cheek and reached behind his head to pull Dip deeper into the kiss.
One of Dip’s hands began to run along her back in return, and the other-Oh, whoops. The other was occupied with the new journal, which he carefully placed on his desk before using the now-free hand to cup her ass. He loved the feel of her soft, warm skin and the rough thinness of the fabric, and even as he lifted her up he ran a daring finger or two underneath the back of the panties.
She broke their kiss to whisper “Yup, you found it; That’s my butt” before breaking into giggles that Dipper joined in. The giggles gave way to more kisses, their mouths locked as her tongue explored his, and his hands went from her back and ass to running along either side of her chest, ending with cupping her breasts and giving them an experimental rub through the fabric.
Mabel moaned into his mouth, but before he could reach underneath, she had drawn back, breaking their kiss with a mischievous smirk. Dipper grinned back, murmuring “What’s with the face? Should I be worried about this face?”
Mabel grinned, and ran her tongue along her lips, something that Dipper had never consciously fantasized about, but was now 100% certain would feature in large part in most of his “personal time” from this point forward. As she pushed him backwards onto his bed with one hand, she ran the other along her chest, cupping her own breast.
As she did that, she teasingly said “You’re not the only one who uses the computer for ‘research,’” she said, as she brought her hands back to flow along her sides, hooking into the edges of her panties as she tugged them to her knees, shimmying a bit until they fell to the floor. She stepped out of them, and pushing Dipper fully flat against the bed, she got up on the bed and knelt astride him.
Dipper was painfully erect, rivalling when they were in the Tunnel that afternoon, and his twin certainly wasn’t helping matters as she rocked back and forth, rubbing herself across his suddenly-accursed-and-unwanted pajama pants. As she rubbed herself on him through the thin, infernally-present fleece, Mabel rubbed her breasts through the teddy, the thin material shimmering back and forth as she rocked her hips, and he could hear her let out a little happy moan as she reached in under one of the outfit’s cups to reach her bare skin.
Dipper groaned at the sight and his own sensations, and muttered “Hey Mabes, I think there’s something in the way. You want me to get rid of it?” His voice rose to an unanticipated pleading pitch near the end as she ground especially hard against him, and he thrust his hips upwards in response.
His sister just nodded, but didn’t move off of him. As Dipper leaned forward to remove the offending garment as best as he could, that brought him up nearly chest to chest with Mabel. She gave him a falsely innocent look, one breast popping out of the now-lopsided teddy, and with a grin and a little growl he dove forward, sucking and flicking her nipple with his tongue.
She responded with a moan of her own, her hands suddenly lifting his shirt up to dig her fingers into his back, pulling her against her. He struggled with his pants, before freeing them to around his knees. From there, he had to flail his legs a bit awkwardly for a minute, but the pants slid off to join his sister’s decorative panties on the bedroom floor.
This time it was Mabel’s turn to let out an appreciative growl, and she began to rub against him anew, her wet lips sliding along the underside of his pulsing shaft as they both gasped. Dipper’s mind was becoming white, pleasant noise, and the only word he could whisper out was a muted “Please.”
It was the only word needed.
She shifted her hips forward, and lifted up off of him for a moment. Dip felt his cock twitch as she grabbed it, and guided it to her lips, before she sat down heavily on him, engulfing his length inside her warmth as she let out a little squeak of pleasure, shimmying her hips slightly to fully seat herself on him.
The shock of the amazing feeling partially restarted Dip’s mind, and he moaned out “Oh god Mabes,”as she began to thrust her hips forwards and back, her hands bracing themselves under his shirt and against his bare chest, the nails tickling and lightly scratching him in the process.
He began to respond in kind, grabbing above her ass and thrusting upwards with his own hips in time, the impact forcing a stilted intake of breath from his sister and a groaning “mmph” from himself with each stroke. The teddy was gorgeous, but now all his mind saw was an impediment to her naked body, and after she helped him out of his shirt, he reached behind her to fumble and unclasp the bra, letting the lacy nothingness fall to the side.
Above him, his sister was now nude, and as close to an angelic form as he could imagine. Her brown curls hung around her head, some plastered to her head and back with sweat, but the others bobbing almost far enough down to provide modesty to her chest. Her breasts were small, but full enough for Dipper’s tastes, and with incredibly responsive nipples that sent Mabel into shivers as he alternately leaned up and sucked each of them.
He had felt shivers and goosebumps down her back when they had first started, but now her back, ass, hips, and thighs were burning, warm and with a thin sheen of exertion on them that matched his own heat. Her taste, as he kissed along her chest and sucked on a finger, was expectedly salty with sweat, but always with that hint of sweetness, that taste that was so completely Mabel that he couldn’t describe it if he tried.
She began to thrust harder against him, groaning out an increasing-in-pitch “Ooooooooooooh-” before he could feel her tightening around his cock.
That set him off, and he could feel himself start to clench. “Mabel-” was all he was able to get out before he exploded, feeling his shaft pulse into her. Her groan abruptly shifted upwards to almost a scream, muffled quickly by Dipper as he darted his head up for a kiss, his mind suddenly aware that their parents were asleep just down the hall.
She spasmed around him, her legs jerking and locking around him as his hips thrust upwards even after he spent his load. After her scream faded, he broke the kiss, and Mabel just made a happy “Mmmmhm, oh yessir, that is a ride Lady Mabeltown would like to ride again once…Whoo, once the world stops spinning.”
He chuckled, and kissed up along her chest to the nape of her neck and under her chin, causing her to shudder and spasm again, and he murmured into her ear “Well, give me a minute to catch my breath and, er, recharge and the ride should be up and ready for business.”
Mabel murmured a noise of approval into his neck, and slid off of him, laying next to him as he lay back along his bed, resting against the pillow with his arm around her. “I love you Mabes,” he whispered, kissing the top of her head as he enjoyed her warmth.
She sighed happily, and replied “Love you too, Dips.” After a brief pause, she added “And I especiallylove your ‘Little Dipper,’” while reaching down to cup his flaccid member and causing him to start.
“Maaaabel,” he said in a voice with more than a bit of a whine in it, and she giggled and threw her arms around him, snuggling against his side and wrapping one of her legs over his. A long day of waterpark fun had combined with their recent coupling, and exhaustion had begun to set in, overruling his protesting libido. He could hear her breathing slow in time with his own, and as he was about to drift unconscious, he heard Mabel, in a voice laced with sleepiness, murmur “G’night brobro.”
He smiled, and the last thing he remembered before drifting asleep was replying “Good night, Mabes.”
- 7
- 8
- 9
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The Tunnel