I realized it might be a bit confusing the placement of the stories. Rin hasn't opened the sword because instead of sending him away, both Shiro and Yukio go with him. The Gravity Falls stuff is before Mabel and Dipper vs the future.

Chapter 4: Keys, keys, keys...Sword?

As the night wound to a close the sheer number of people now staying in the Mystery Shack forced the twins to double up. Rin and Yukio, much to the latter's protesting, had to share a room with Dipper and his boy crazy sister. After the whole 'their father is a demon' reveal she had lost all romantic interest in Rin, directing all of it to his glasses wearing brother. That didn't mean the older twin was off the hook, like this Dipper had all the time in the world to ask him as many questions as he wanted to.

He clicked the pen in his hands a few times, trying to decide which question to start with. Rin was sitting on his bed, facing the smaller boy, but with his eyes on Mabel who was flirting incessantly with Yukio. He noticed a look that passed between the two boys, something like sympathy and irritation. Mabel was to distracted to notice Yukio mouth, 'save me,' in their direction.

"So, uh… Dipper, did you know that Yukio already has a girlfriend?"

Not sure if the teen was lying or not, Dipper played along. "No… What's she like?" He could see the wheels turning in Rin's head, so clearly he was making it up.

"Well, she really sweet, short blonde hair, loves plants… nice rack, an-"

"Rin!" Both Dipper and Yukio's older twin turned, very startled. The young man's face had gone completely red and he was glaring at them. "D-don't talk about Shiemi like that… Wait, how do you even know about her!?"

Rin had a confused look that flickered into a mischievous grin, "I know you too well," his brother seemed more annoyed than embarrassed now. If Dipper had to take a guess, Rin had just put together features his twin liked and it happened to describe a real person Yukio knew.

Mabel who only just seemed to notice where the conversation was going looked hurt then curious, finally landing on a 'fan girl' face. "What's your relationship like," she gasped in a big breath of air, "No! is it possible you're both in love with the same girl?!"

Dipper looked from Rin to Yukio, they were staring at each other, he could swear there was lightning passing between. The younger wore seemed to be saying 'look what you've done!' while Rin had a 'sorry for trying to help,' expression, adorned with a sarcastic smirk. Mabel was going crazy with her own story about the twins' love lives. "You do realize they're only three years older than us, yeah Mabes?"

"Yes, Dipper! Three whole summer's worth of romance more than me! I need to know!" She sprung up on the bed jumping up and down.

"T-there's nothing to know!" Yukio lifted his hands in a calming gesture, attempting to get Mabel to settle down. Rin just his eyes, grabbed up one of her pillow from the floor and launched it at her head. There was a soft thwump and she landed on her stuffed animals. Once it fell off her face she was left staring wide eyed at Rin. Dipper, seeing where this was going scooted back before Mabel could retaliate.

Any hope of getting answers was off the table, Mabel had leapt up again, a pillow raised above her head, "This means war!" The white, fluffy object went hurtling towards Rin's face and he ducked just in time, so it hit Dipper instead. Rin looked at him and smile, Dipper smiled back and it turned into a battle royal style pillow fight. Yukio, to his credit was trying to get everyone to settle down, until Rin tackled him and stole his glasses, running around the room holding them up and laughing hysterically while his younger twin chased him, pillow in hand.

By about eleven the four of them were all sprawled out on the ground laughing and utterly exhausted, the struggle had been legendary. Allegiances were switched several times and the room was covered in feathers. Only Mabel's pig was left standing. Rin, laying on his back, lifted Waddles into the air, and with the deepest voice possible declared, "Behold, Waddles the conqueror, victor of the epic Pillow War!" Yukio, who had seemed very uptight, even more so than Dipper laughed, as did everyone else. Dipper didn't stay awake long after that, Rin seemed to have passed out just after saying that, Waddles dropping onto his head.

When Dipper blinked awake the next morning, after one his most peaceful night sleeps since coming to Gravity Falls, he realized his pillow was moving. Followed quickly by the noting that it wasn't a pillow but Rin. In fact it seemed that everyone was sleeping on Rin in some fashion, Mabel had a pillow propped up against his leg, Yukio's head was on his right shoulder, and Waddles hadn't moved from last night. Rin's mouth hung open and he gave a low snore every third breath. The smaller boy struggled to sit up, the teen's left arm trapped him, impossibly strong even in his sleep. Dipper grunted and heaved, freeing himself from Rin's grip. His hand seizing the nearest thing, one of Mabel's stuffed animals, and pulling it into the position Dipper had just vacated.

The youngest, and only awake, twin noted a metallic gleam under his new friend's shirt. The key he'd asked about yesterday was resting unguarded and Dipper found it near impossible to contain his curiosity. Certainly a little peek wouldn't hurt, he did just want to know why it was so important. Very carefully the brunette boy slid forward and picked at the loop holding the golden trinket to Rin's neck. Once it was free, Dipper slipped it off and took a good three steps back, examining the simple object. It looked like a dresser key but surely, if you had something to keep safe you'd bring the container, not just the method of opening something.

As he thought about it, the twelve year old remembered seeing both Yukio and Shiro with a large collection of keys. Was it something to do with being an exorcist, like a protection charm? Did it serve some purpose that was mystically fulfilled? They battle demons on a regular basis so perhaps they were some kind of weapon or tool? "Like a storage device?" Dipper murmured to himself, glancing around the attic.

In the corner stood a very old chest of drawers with one such drawer adorned with a keyhole. Figuring that this was the best time to test his hypothesis, Dipper carefully stepped over the other's sleeping forms and positioned the key. He took a sharp breath, not really knowing what to expect. The tumblers clicked easily with the key's turn, like it had been specially made even though that was actually impossible. When he pulled the drawer out the inside was covered in a red velvety lining. Resting in the shallow space was an antique Japanese sword, a seal plastered over the hilt, similar to the ones Shiro had placed in the house, completely burned through. "What does a sword have to do with this?"

Dipper perused the space a bit more before turning his inquiries fully to the blade. Initially, and most glaringly obvious, was the dimensions of the drawer. The inside was two inches wider and three inches shallower than the actual measurements. Next was the wood, the chest was made from oak but the visible frame seemed to be maple of some kind. Opening another drawer to compare the interiors showed the furnisher to be rather plain in style as opposed to the rich velvet material. The key, Dipper reasoned, would fix any lock and always open this drawer, regardless of what the physical object really contained, kind or like Schrodinger's cat.

Something snared Dipper's attention, though he couldn't identify it, outside the sword's general existence. He lifted his hand, hesitantly brushing his fingers over the worn scabbard. His entire body froze, a low beat thrumming in his ears, pulsing under his fingers. The sword was alive, breathing in time with Dipper's heartbeat. Startled, he yanked his arm back, holding his wrist in his hand, a collection of blue sparks falling from his fingertips. "W-what was that?" Rin's words from the day before rung in his ears, the revelation of the teen's demonic heritage adding meaning to his warning. "This sword… is Rin?" Disgust boiled up in his throat and he shoved the drawer shut with a loud thump, practically ripping the key out of the keyhole.

"Terrifying, isn't it?" Dipper jumped, he hadn't even noticed Yukio behind him. The older boy's eyes were filled with understanding and he placed a hand on Dipper's shoulder, "Can I trust you?"

"I… uh, I-I'm sorry. I shouldn't have taken this," he held the key out but Yukio pushed his hand away.

"Give back to Nii-san; he's the one you need to apologize to, not me."

"These keys… They bend space don't they?" Yukio simply nodded, "I see… Do you think Rin will even want to forgive me?"

"He's a very straightforward and honest person, he likes to see the best in people. If you're truthful with him, I've no doubt he'll forgive you."

"Thanks…"

The older boy yawned, well I better get downstairs, father will want me to check the wards to see if they're still working."

Dipper stuffed the key into his vest pocket while he rushed to get dressed, Yukio even at a more leisurely pace still dressed in his combat jacket and fully armed before the smaller boy had gotten his hat on. "Do you mind if I watch?"

"Not at all."

*POV

Rin shifted uncomfortably, his leg was asleep and there was something warm and heavy pressing on his face. "Urg," he sat up, Mabel's pig falling into his lap, "oh that was you, Waddles." He heaved a yawn and stretched, the pig's owner groaning in her sleep, lounging against his leg. "Well that explains it. Hey Mabel," he poked her face gently until she started to wake up, "it's time to get up. Hey, Ma~bel… Ma~bel, hey," he shook his leg and she jolted awake, eyes wide in surprise.

"R-Rin?"

"Morning sleeping beauty." He grinned gently at her alarmed face, not quite sure what to do. Waddles finally decided to get off him and with Mabel no longer leaning on him, Rin could stand. He hoisted his arms above his head and lifted himself onto his toes, an enthusiastic yawn pulled from his mouth.

"Where did everyone go?"

"Hm… Yukio's always been an early riser, guess Dipper was awake and they went downstairs…" Waddles squealed and snorted, sniffing Rin's leg. He knelt down and gently lifted the pig up, hugging it. Mabel must have thought it funny or cute cause she was reduced to giggles, and he had to admit her laugh was infectious. "Hey, do you normally make breakfast?"

"Yeah… do you?" He nodded and a wide smile broke over her face. "Wanna cook with me?"

"Yes! I was hoping you'd say that," finally something he could do well, and be normal at. The ran downstairs, not bothering to change out of their pj's. "I got the omelet, you wanna make pancakes?"

"Definitely, I make a pancake to die for," she cheered holding a whisk up like a sword. Rin couldn't help but laugh, she was the cute little sister he'd never had. They were laughing and mixing, baking and sauteing, flipping and folding, Mabel flicking batter at Rin from her whisk whenever he'd make a particularly funny joke. "Oh you are just horrible," she chuckled when she say him balancing an egg on a spoon in his mouth, flitting back and forth from the stove, where his omelet was setting together nicely, and the table where he was setting places.

He grinned at her around the metal between his teeth, flipping the omelette over. Breakfast should be ready soon. The siren call or smell of the food summoned the rest of the Pines family and Rin's family to the kitchen. "Look at this," he placed the egg on the counter, spinning it on it's tip. He placed his pointing finger on the other end, blue sparks flying for only three seconds before he knocked the egg into the, slicing it in half in the air. Rin caught the two halves in his other hand, showing off a perfectly scrambled egg. Mabel gasped of course demanding to know how he did it, "Ahhaha, a magician never reveals his secrets, Mabel."

"Gah, that's so cool though!"

"Just wait till you try Nii-san's cooking," Yukio and Shiro had both moved into the kitchen table, claiming seats.

"Stop trying to butter me up foureyes," he faked a sarcastic tone, ruffling his brother's hair. He knew exactly what they'd want, adding some of Mabel's pancakes for good measure. When he saw the other three members of the Pines clan awkwardly standing in the doorway he pointed at them, "Are you going to stand there gawking or come eat?"

"You'd better hurry," Shiro spoke between mouthfuls of breakfast fare, "or there won't be anything left." With that prompting everyone crowded in snatching food off of the serving plates being passed around. Conversation varied from the weather, to plans for school, to the best way to take down demons, gnomes, unicorns, and the like. Laughter and family became the whole world and for half an hour, Rin was happier than he'd been for a long time. His weirdness fit in in Gravity Falls, and he could be himself, freakishly strong and kinda clutzy, and the Pines just went with it.

"Hey, Kid, would you mind me using you as an attraction today?" Stan said with a jovial laugh, "All you have to is stand around and hold something heavy!"

"I-uh," he desperately glanced to his brother and father, getting a shared look of 'staying out of this', "I guess, for a bit…"

Dipper was shaking his head, waving his hands through the air, only to plant one on his face when Rin agreed. He raised a brow in confusion at the younger boy's antics.

\\

"Um, so, like this?" Rin asked, a stack of weighted boxes in his arms.

"Yeah, perfect. Now just stand there for ten hours."

"Wait, what?!"

Rin glared at Stan as he walked away, feeling altogether indignant. He didn't have time to yell anything obscene at the old man because he was suddenly surrounded by people taking pictures and chattering at him. His head was spinning from all the question. One very large and hairy, redhead lumberjack walked up to him, "Ha, this is just another of Stan's charades isn't it? How much do those boxes weigh, kid?" His breath smelled like a gym locker and the way he loomed over Rin really pissed the teen off.

"One hundred pounds each, and my name is Rin." He clenched his teeth, stopping himself from adding any colorful language.

"Sure they are," the lumberjack went to pick a box off the top of the stack, his eyes widening as he realized Rin had been truthful. "T-they really are that heavy?"

Rin scoffed and shifted his remaining bundle into on hand, holding out the other, "Can I have my box back now?"

"Sure," he had a sheepish expression on his face, "you're really strong, kid! Feel free to come to our manly club any time." With a rolling mountaineer laugh the giant of a man walked away. Unfortunately for Rin, the man's verification of the weight only increased the number of people pushing in to get a better look.

As the day lagged on Rin had to deal with awkward conversation, sweaty people pressing in at him, the glaring sun, because he was standing outside the Mystery Shack, and Stan adding more of the weighted boxes. His arms were starting to go numb after about three hours, he kept shifting the pressure from one hand to another. Mabel came to talk to him when the rush slowed and Dipper passed him water bottles every now and then. Nothing much happened until one little girl, a tourists daughter, started kicking him in the shin trying to get him to drop the boxes. Her mother was absorbed in shopping and her father wasn't paying any attention to something not his phone. "Cut it out," Rin snapped at her. The pintsized brat kept laughing and he'd had it, two hours ago.

Rin's foot slammed into her chest, sending the little monster tumbling away, a glare on his face. She wasn't at all hurt by the shove, but when she looked up into his face tears sprung from her eyes. It was strange, children cry to get attention but she was deathly silent. When she screamed in terror the teen realized his eyes must have changed. Everyone who was present immediately turned to the little girl, her father snatching her up and backing away from Rin with the same terror on his face. The boxes crashed to the ground and Rin sprinted inside, not stopping until the attic door slammed shut.

The room was just as it'd been this morning, a mess. Rin's back pressed against the closed door and slid down to the floor. "I fucked up again," he muttered, curling up to quietly berate himself. Dipper pushed the door open just enough to see him.

"Hey," the younger boy's voice was gentle, "what's wrong?" Rin looked up at Dipper's face and he flinched, "Oh." He pushed the door against Rin's back again and the half demon got out of the way. Once the pre-teen had shut the door behind him, he too sat down on the floor, staring at Rin. "Want to talk about it?"

Rin heaved a sigh and went through his most memorable irritants ending with the little girl, "I didn't hurt her or anything just… freighted her… " he pulled himself into a ball, groaning at his sore shoulder, "I just … don't want to be a monster."

"Whenever Mabel or I go through a hard patch we have each other. Since Yukio isn't here," Dipper stood up and hugged Rin, saying, "Awkward not sibling hug. Pat. Pat." He let go once Rin started laughing.

"You do that?"

"Yep."

"Thanks Dipper," he wiped a jolly tear from the corner of his eye, "I'm feeling a lot better."

"Glad to hear it." The pre-teen smiled at him. Yeah, Rin liked it here. Sure there were problems, but there were always problems, what matters is how you deal with them.

Stan's voice cut through the moment, "Where did he go? You're costing me $50 a minute!"

And done. Yay, it's a nice chapter! Bad things are going to happen soon :D