Dipper Adula Pines ran through the forest with his Sunstone sister by his side, weapons out and at the ready. They were perfectly in sync with each other, just like they had always been, traveling separately to avoid a clumsy misstep wasting their time, but close together as always.
To an outsider standing in the trees and out of the way, they would seem to be nothing but two beams of fluid light cutting through the twilight. The twins shots twirl around each other as if in a dance, but they, and their target, knew better.
For once, the kids traveled completely silent of all banter.
It was serious time.
A monstrous roar sounded through the trees, scaring a flock of eye-bats into the sky.
Mabel looked at her brother for further instructions, and was greeted with military sign language. Neither of them had any time to ponder how they themselves could make/understand what a piece sign and couple of finger loops meant (they each dismissed the other's knowledge to movies and books, respectively), before they simultaneously did what Dipper suggested and split up.
Grunting, growling, and now quite tired out of its rampage through the woods, the 'corrupt' gem knocked down a couple of trees before it patrolled around its newly-made clearing. It was cornered and trapped, chased down like a stupid animal, and now, it was angry. Angry and scared.
Dipper locked eyes with Mabel across the clearing, both perched on perfectly identical branches.
"HIYAAAA!"
They jumped and tackled the monster simultaneously. This backfired though when the twins hit each other mid-air and fell back groaning, gem weapons disintegrating into glittering sparks.
The owl-gorilla monster glowered down at them, its jet black fur spiking up in agitation. From its beak-maws came a roar loud enough to shake the earth itself.
Then the roar dissolved to laughter. The laughter of an old man, to be exact.
"I thought siblings are supposed to be good at all this, egh, 'working together' stuff, huh?" Grunkle Stan chortled, reverting back to his default form. The twins groaned again in tandem and got to their feet, sighing. Their new costumes, now dirtied with grass stains and smears of mud, shapeshifted into their normal clothes – uniformed attire as always for Dipper, and a green-haired troll sweater for Mabel. Their skin bled to a healthy peach color. Their hair darkened to brown. Grunkle Stan rolled his eyes at their matching downtrodden looks and sighed.
"Don't sweat it, kids. I'm sure you'll be able to get better, till you can get me easy in no time at all!" He planted both palms firmly on top of the siblings' heads, making them snort and giggle and reach up to flick his wrinkly hands off.
"I bet I can still beat Dipper though," Mabel snorted, to which her brother replied with a scoff and by flipping her hair over her face. Stan laughed heartily as the kids devolved from playfully kicking and slapping each other to full-out brawling in the grass in front of him.
"As if! I can so whoop your butt!"
But then the mirth of the moment faded. Grunkle Stan's face softened, chuckles tapering off. "Hehe! ...Huh," The old man stared after his family and gained a faraway look in his eyes. His lips twitched into a ghost of a wistful smile weathered by time and age. He murmured quietly, internally intent on grabbing onto this happy time – this ordinary, cheerful Summer day – as much as he could store in his memories –"In no time at all."