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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
- 6
- 7
- 8
Dipper had to admit; He was impressed. Mabel had managed to keep the primary reason she’d wanted him to come to Watermania so badly a complete secret. While he had restrained himself, with no small amount of difficulty due to how ingrained investigation was into his instincts, and had suspected something was up, he certainly wasn’t expecting, well, this.
The ride complex was covered and large; It looked like they’d built a substantial warehouse, decorated lightly on top with some foliage and foam tree trunks, in a mild attempt to make it look like a forest-covered hill. The entrance itself was an unassuming little lazy river, much like the one the Terror had spat them out into, with a yawning lifeguard sitting near a control panel with a trio of buttons on it.
“Um, that’s a, uh, very comfortable boat setup they have there,” he murmured to his sister as he caught sight of one the rafts themselves, as it emerged from the exit. The couple inside it had barely noticed their raft had exited until it bumped against a submerged stop railing, and the men clambered out with a bit of a sheepish smile on their faces towards the lifeguard and the twins before they wandered off with a hand around each-other’s shoulders.
The rafts themselves were painted and shaped to look like Venetian gondolas, albeit shorter and wider and with heavily padded edges at the waterline. Looking back, he could see only two fairly-wide seats in the gondola itself, facing each other just a few feet distant; Perfect for gazing into a lover’s eyes, I suppose, he thought wryly, before the thought returned a second later to poke him with a reminder:You and Mabel aren’t lovers, though.
Dipper blushed a bit as an indignant, hopeful bit of him rebelled against logic and common sense. You mean we aren’t lovers YET.
That thought, and a merry stream of implications and resulting string of momentary minds-eye daydreams about a warm body, writhing in his grasp, hot and responsive to his touch, moaning his name…well, that stream of thought very quickly had Dipper awkwardly coughing and trying to adjust his woefully-insufficient swim trunks again as Mabel clambered into the Gondola..
She then glanced over at his distress, quizzically at first, but then giving him that little taunting and mischievous smile when she noticed his erection. As her arm raised towards him, Dipper could feel an abrupt cold sweat down is back.
Ohhhh, nonono, Mabel, now’s not a good time, the lifeguard’s right there and looking at us and ohhhh not yet not yet please not yet-
His sister had apparently heard his unconscious pleas for decorum, or maybe she noticed his face turning cherry red, but in either case her hand made an abrupt veer in direction to one side to grasp his arm, and tug him onto the boat.
As he sat, the lifeguard began reciting the general spiel about safety, keeping arms legs and possessions inside the boat at all times, and to not exit the boat until it came to a complete stop at the end of the ride. Dipper and Mabel shared a brief momentary eye-roll, but nodded, and with the press of a button, the stop rail clacked out of place, and they began to float forward.
The gondola passed through a trio of shimmering tinsel curtains, and briefly looking back, the natural daylight faded as they went around a corner. He was taken aback by the interior, since the appearance outside had been underwhelming. Here, though, the boat was travelling through an area that, through forced perspective, looked like they were on a hill, overlooking a small, sleepy town below.
Heck, he thought as he watched the light fade to a rosy sunset, lights winking on in the little paper buildings, If you squint, add a water tower, and add the split ridge in the distance, it’s not too far off from Gravity Falls.
He smiled, but glancing back to Mabel he saw her staring at him, seemingly ignoring the little picturesque scene next to them. He gave her a smile, and she returned it partially, but he could see something was bothering her; Her shoulders looked stiff, her pose tense, and she had a look in her eyes like she was both ecstatic and terrified.
She stood up abruptly, the boat rocking back and forth a bit, and Dipper let out a “Whoa!” as the gondola rocked, but his sister had ignored the rocking and was now standing in front of him. He could see her shoulders going up and down now as she took little quick breaths, and a second later she closed her eyes, taking a long, steadying breath, before letting it out and opening her eyes.
Dipper had a moment of confusion, and then a white-hot lightning bolt of realization and anticipation as Mabel crouched to kneel on the plastic fake-wood floor of the gondola in front of him. His dick, which had softened significantly when the day-dreaming abated, suddenly reawakened with a vengeance, but Dipper’s mind was a flurry of two streams of thought, fighting each other loudly for his attention as he gave his sister a grin tinged with nervousness, but loaded with unspoken anticipation.
Mabel, sis, you don’t need to do this, really-
-But hey, if you do want to do this, I am 100% on board with this all the way no questions asked-
-I don’t want you to feel like you’re obligated to do this since you should know I love you no matter what you do or don’t do-
-Man, but if you want to do this, I would love to do this with nobody but you and your amazing body. I mean, hell, you gave me a boner faster than I’d ever had before-
-This is so wrong, though, like something you’re never supposed to do-
-But it feels so amazingly right, like everything is lining up like it feels like it should-
-I don’t want to ever hurt you or break the trust we have-
-So please don’t think I hate you and want you to stop-
-Don’t do this if you’re not sure-
-I love you with no exceptions-
-Be true to yourself-
-Be my everything-
-Please-
-Please-
“Please.”
The roaring of his thoughts culminated in the one little groaned word, and Mabel smiled, and reached up to pull his head down to hers, and brought her beglittered lips up to touch his, gently and almost teasingly, before breaking it. His breathing began to get irregular, short, as he watched her lead kisses down his chin, his bare chest, his little happy trail Which was no easy task to grow, mind you, before finally kissing the top of his cock through the moist fabric.
His hips twitched as he clenched his eyes shut in ecstasy; He had never gone farther than kissing and a little bit of heavy petting with Pacifica or his other brief attempts at having a girlfriend, and thiswas never something he’d have imagined becoming a reality in a thousand years. Hell, this was better than any of his own fantasies of the scenario had ever been, and now there was no worry that something weird, like Grunkle Stan barging in wearing Waddles’ head, was going to happen like what would interrupt his otherwise-happily-erotic dreams.
The baselessly paranoid part of Dipper’s brain poked him to open an eye and glance around quickly for a porcine grandparent. The tunnel scene had shifted to an emulation of a lazy bayou, weeping willows leaning their soft branches into the water on either side and forming a green canopy the boat drifted through.
Mabel gave him another little kiss through the fabric, causing him to twitch again, and then reached up to the zipper and began to slide it down.
Or at least tried to. It was decorative, and she tugged a few times, “hmph!”-ing with frustration after it failed to yield, and Dipper couldn’t help but chuckle. He hooked his thumbs into the sides of his shorts, and began to slide them off; Not without a small amount of effort, due to the tension of the shorts on his bony frame.
As he pulled them down, he slowed, apprehension plaguing him again despite everything that had happened so far. Mabel showed no such hesitation, giving him a slightly annoyed look that was quickly smothered in muted excitement, and she yanked them down to pool around his ankles, revealing his cock to the suddenly-slightly-too-cold air of the ride.
It twitched to one side, and Mabel grabbed it. The feeling of her hot, soft hands on him caused him to twitch again and let out a little happy groan of her name. “Mabel…”
She smiled, leaned up to give him a peck on the cheek, and then leaned back down to engulf him in her mouth.
Holy MOSES-
Dipper let out a moan of pleasure, and Mabel replied with a happy hum. As she still had him fully in her mouth, this had the effect of buzzing his cock in an indescribably pleasant way, and he arched his head back, running a hand through her hair before gripping it as his other hand sought a handhold on the smooth side of the gondola.
She made a startled noise as he gripped her hair, and for a second he let go, but before his wrist could migrate away from her, her hand grabbed his, and led him down to the smooth cloth of her bikini top. He smiled, and began running his hand around and along the fabric, feeling her nipple perk up under the fabric as she made a happy moan, again resulting in a buzz on his cock that was heavenly.
He slipped his hand under the fabric, and gave her a gentle squeeze, running his thumb across her nipple and revelling in feeling her shiver with delight. In response, she began running her tongue along the underside of his shaft, causing his hand to freeze as he tried to concentrate all brainpower on burning that feeling into his memory, but more importantly remembering to breath and not pass out.
Then she began sucking, and he could see her hand dive towards her bikini shorts, as her breathing became quicker, panting on his member and occasionally releasing him from her mouth and running her tongue across the tip of his cock before diving back down to engulf him again.
Dipper shuddered, and with a moan of “Oh god, Mabel, I’m-” he could feel his balls clench. Mabel abruptly stopped with her tongue, but continued rubbing herself furiously, and was sucking him harder than before as he came. He could feel the spurting warmth, and could feel her continue to suck, her breathing long and labored as she sucked and swallowed his seed.
After what seemed like a glorious eternity, prolonged by Mabel’s continued sucking even after he stopped cumming, Mabel released him with a wet popping noise, sucking in a breath followed shortly by a giggle. The giggle merged directly into a moan, as she hunched over, her shoulders shaking as Dip could see her hand working furiously beneath the suit.
Unsure of what to do for a moment, Dipper abruptly grabbed his sister’s hand by the wrist, tugging it gently but insistently away from her. As she looked up, saying “Dipperrr…” with a sad longing groan, he knelt down in the rocking gondola, and kissed her on lips still tasting faintly of vanilla-bean.
He could feel her mold to his body, and his spent cock gave an appreciative twitch as their nearly-nude bodies pressed close, indicating that it’d be up for another bout of fun after a quick breather. Dipper hugged Mabel close with one hand, but snaked his other downwards, running a finger down her chest and causing her to moan as he slid under the fabric of the bikini and along the tip of her lips.
C'mon porn, tell me all that ‘studying’ was worth it. He ran a finger along her lips, questing it occasionally between them, each time resulting in her making an appreciative happy noise. Finally, he found what he was looking for, and ran his finger in a little circle around her clit.
The response was immediate, with Mabel choking out “Ohgod” and smashing her lips against his, thrusting her tongue inside his mouth with a passion that took him momentarily aback. Her hips shook, and her thighs clenched against his hand as he continued to run his finger in little teasing circles, before he finally rubbed it firmly with the pad of the finger.
That hit the spot apparently, as his sister arched backwards, eyes wide open, her mouth open to let out a prolonged, strained “Oooohhhhh” that transitioned into a clenched-teeth squeal of pleasure. He pulled his hand away, encouraged by her own hand as she sat back alongside him on the wide seat. They were both panting, although Mabel seemed like she’d just ran two marathons to Dipper’s one, and she said in a happily exhausted voice “Aw man, Dippingsauce, where did you learn that?”
He looked aside, suddenly slightly embarrassed, and his twin just chuckled and punched him in the arm. “Doofus, I kinda figured you’d seen ‘instructive cinematography.’ But, I mean…wow, did you ever get a chance to practice that in person before?”
Dipper flushed, and with a tight-lipped expression, shook his head. Mabel looked towards him, compassion and a tinge of rising excitement coloring her gasping out “So you mean that was your first-” and letting the unspoken words hang there. Dipper stared at her, abruptly wishing he could have his own sweater and escape this interrogation, but shook his head again before looking down at the false-wood floor.
Mabel let out a happy squeal, and hugged him close, turning to kiss his surprised face on the lips before nuzzling his nose with hers. With a quiet, confident murmur she said “Gotta say, that was both the first time I’ve ever been touched down there by anyone but Yours Truly, but that was also-whooo, that was also the best time I’d been touched down there, including by Yours Truly.”
Dipper let out a wry grin, but the distant sounds of laughter and splashing brought both of their attentions up to the light at the end of a long straightaway. There was another shimmering impermeable curtain of tinsel, but the corridor was lined with mirrors on all sides, reminding Dipper and Mabel of their discarded clothing and general disheveledness.
The next sixty seconds were a scramble of activity as Mabel tried and only partially succeeded in straightening out her orgasm-induced cowlick, while Dipper nearly capsized the boat trying to struggle back into his squeeze-cage of a swimsuit.
They made it and both sat with barely a few seconds to spare, hands interlaced as they gave each other a loving look, and as they went through the shimmering curtain, the twins leaned in to meet in a warm kiss, savoring it for a moment even as the curtain fell away. The kiss broke off as the sounds and lights of the outside world came blaring back at full force, and they stepped off of the ride, and began to walk towards the rest of the park.
They’d scarcely gotten a few hundred feet from the Tunnel when they heard the echoing cries of“Doods? Dooooooods? Oh, hey, doods! DOODS!” and the commotion from a crowd as Soos’s sounds of “Excuse me” and “Oh, my bad” could be heard as he made his way through the press of bodies. He popped out on the other side, a startlingly horrible Bear-O under one arm, and a “Week of Wet!” watergun the size of a small toddler under the other.
“So, what have you two doods been up to?” Dipper froze, and shared a look of barely-concealed mutual terror with Mabel, as the Tunnel was directly behind them and visible from where they all stood. He could feel his chest start to tighten as his mind raced. You didn’t check the damn map, and this section is brand new. Oh shit, oh shit, any second now and Soos will see the Tunnel and put two and two together to-
“We went on Ninjapede Falls!” Mabel exclaimed, startling Dipper out of his tailspin of worry, and he looked over to see her pointing at a black-and-brown rollercoaster that ran through curtains of water. Soos nodded with solemn approval, saying “Oh, good choice doods. I’ve heard that one comes very highly recommended.”
Dipper began to laugh, mostly with relief, and Mabel joined in when they and Soos jumped in terror as the sky flashed, and the darkening clouds boomed with a peal of thunder. A few seconds later, a voice crackled over the loudspeakers, saying tinnily “Due to inclement weather, Watermania is now closed. Please file to the nearest exit, remembering any belongings left in lockers. Thank you, and since we are closed for the rest of the season, see you next summer!”
Soos’ shoulders sagged with disappointment as a spit of rain began to stain the dry pavement, and Dipper could feel a distant pang of regret at not having tried all of the rides this trip. Still, when he looked over at Mabel, that concern washed away with her smile, and she gave a little shrug of her shoulders. “Well brobro, I guess we could always come back next year and make sure we rideeverything.”
Her tone was innocent, and had Soos nodding in agreement as he fished the car keys out of his pocket, but her tone and the mischievous look in her eyes made it perfectly clear that she included her dear brother in the list of “rides,” and that had his heart racing with anticipation.
As they began the walk to the parking lot, Mabel reached out and grabbed Dipper’s hand; He tensed and started to pull away, what with Soos so near, but then relaxed as he remembered that they did this all the time before all the wonderful events of today. Ahead of them, Soos called out over his shoulder “Still doods, bit of a bummer that the trip got called on account of rain so soon.” Dipper nodded, but couldn’t help but think:
You know, I think this excursion was cut short at the perfect time.
- 6
- 7
- 8
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The Tunnel